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Zhang N, Yang X, Su B, Dou Z. Analysis of SARS-CoV-2 transmission in a university classroom based on real human close contact behaviors. Sci Total Environ 2024; 917:170346. [PMID: 38281642 DOI: 10.1016/j.scitotenv.2024.170346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/29/2023] [Accepted: 01/19/2024] [Indexed: 01/30/2024]
Abstract
Due to high-population density, frequent close contact, possible poor ventilation, university classrooms are vulnerable for transmission of respiratory infectious diseases. Close contact and long-range airborne are possibly main routes for SARS-CoV-2 transmission. In this study, taking a university classroom in Beijing for example, close contact behaviors of students were collected through a depth-detection device, which could detect depth to each pixel of the image, based on semi-supervised learning. Finally, >23 h of video data were obtained. Using Computational Fluid Dynamics, the relationship between viral exposure and close contact behaviors (e.g. interpersonal distance, relative facial orientations, and relative positions) was established. A multi-route transmission model (short-range airborne, mucous deposition, and long-range airborne) of infectious diseases considering real close contact behaviors was developed. In the case of Omicron, the risk of infection in university classrooms and the efficacy of different interventions were assessed based on dose-response model. The average interpersonal distance in university classrooms is 0.9 m (95 % CI, 0.5 m-1.4 m), with the highest proportion of face-to-back contact at 87.0 %. The risk of infection of susceptible students per 45-min lesson was 1 %. The relative contributions of short-range airborne and long-range airborne transmission were 40.5 % and 59.5 %, respectively, and the mucous deposition was basically negligible. When all students are wearing N95 respirators, the infection risk could be reduced by 96 %, the relative contribution of long-range airborne transmission increases to 95.6 %. When the fresh air per capita in the classroom is 24 m3/h/person, the virus exposure could be decreased by 81.1 % compared to the real situation with 1.02 m3/h/person. In a classroom with an occupancy rate of 50 %, after optimized arrangement of student distribution, the infection risk could be decreased by 62 %.
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xueze Yang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Hong Kong, China.
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2
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Atamer Balkan B, Chang Y, Sparnaaij M, Wouda B, Boschma D, Liu Y, Yuan Y, Daamen W, de Jong MCM, Teberg C, Schachtschneider K, Sikkema RS, van Veen L, Duives D, ten Bosch QA. The multi-dimensional challenges of controlling respiratory virus transmission in indoor spaces: Insights from the linkage of a microscopic pedestrian simulation and SARS-CoV-2 transmission model. PLoS Comput Biol 2024; 20:e1011956. [PMID: 38547311 PMCID: PMC11003685 DOI: 10.1371/journal.pcbi.1011956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 04/09/2024] [Accepted: 02/29/2024] [Indexed: 04/11/2024] Open
Abstract
SARS-CoV-2 transmission in indoor spaces, where most infection events occur, depends on the types and duration of human interactions, among others. Understanding how these human behaviours interface with virus characteristics to drive pathogen transmission and dictate the outcomes of non-pharmaceutical interventions is important for the informed and safe use of indoor spaces. To better understand these complex interactions, we developed the Pedestrian Dynamics-Virus Spread model (PeDViS), an individual-based model that combines pedestrian behaviour models with virus spread models incorporating direct and indirect transmission routes. We explored the relationships between virus exposure and the duration, distance, respiratory behaviour, and environment in which interactions between infected and uninfected individuals took place and compared this to benchmark 'at risk' interactions (1.5 metres for 15 minutes). When considering aerosol transmission, individuals adhering to distancing measures may be at risk due to the buildup of airborne virus in the environment when infected individuals spend prolonged time indoors. In our restaurant case, guests seated at tables near infected individuals were at limited risk of infection but could, particularly in poorly ventilated places, experience risks that surpass that of benchmark interactions. Combining interventions that target different transmission routes can aid in accumulating impact, for instance by combining ventilation with face masks. The impact of such combined interventions depends on the relative importance of transmission routes, which is hard to disentangle and highly context dependent. This uncertainty should be considered when assessing transmission risks upon different types of human interactions in indoor spaces. We illustrated the multi-dimensionality of indoor SARS-CoV-2 transmission that emerges from the interplay of human behaviour and the spread of respiratory viruses. A modelling strategy that incorporates this in risk assessments can help inform policy makers and citizens on the safe use of indoor spaces with varying inter-human interactions.
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Affiliation(s)
- Büsra Atamer Balkan
- Quantitative Veterinary Epidemiology, Wageningen University & Research, Wageningen, The Netherlands
| | - You Chang
- Quantitative Veterinary Epidemiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Martijn Sparnaaij
- Department of Transport & Planning, Delft University of Technology, Delft, The Netherlands
| | - Berend Wouda
- Gamelab, Delft University of Technology, Delft, The Netherlands
| | - Doris Boschma
- Gamelab, Delft University of Technology, Delft, The Netherlands
| | - Yangfan Liu
- Quantitative Veterinary Epidemiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Yufei Yuan
- Department of Transport & Planning, Delft University of Technology, Delft, The Netherlands
| | - Winnie Daamen
- Department of Transport & Planning, Delft University of Technology, Delft, The Netherlands
| | - Mart C. M. de Jong
- Quantitative Veterinary Epidemiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Colin Teberg
- Steady State Scientific Computing, Chicago, Illinois, United States of America
| | | | | | - Linda van Veen
- Gamelab, Delft University of Technology, Delft, The Netherlands
| | - Dorine Duives
- Department of Transport & Planning, Delft University of Technology, Delft, The Netherlands
| | - Quirine A. ten Bosch
- Quantitative Veterinary Epidemiology, Wageningen University & Research, Wageningen, The Netherlands
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Haowei Y, Mahyuddin N, Bin Nik Ghazali NN, Wang Z, Liu Y, Pan S, Badruddin IA. A critical review of research methodologies for COVID-19 transmission in indoor built environment. Int J Environ Health Res 2024:1-65. [PMID: 38385569 DOI: 10.1080/09603123.2024.2308731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/17/2024] [Indexed: 02/23/2024]
Abstract
The Coronavirus Disease 2019 (COVID-19) has caused massive losses for the global economy. Scholars have used different methods to study the transmission mode and influencing factors of the virus to find effective methods to provide people with a healthy built environment. However, these studies arrived at different or even contradictory conclusions. This review presents the main research methodologies utilized in this field, summarizes the main investigation methods, and critically discusses their related conclusions. Data statistical analysis, sample collection, simulation models, and replication transmission scenarios are the main research methods. The summarized conclusion for prevention from all reviewed papers are: adequate ventilation and proper location of return air vents, proper use of personal protective equipment, as well as the reasonable and strict enforcement of policies are the main methods for reducing the transmission. Recommendations including standardized databases, causation clarification, rigorous experiment design, improved simulation accuracy and verification are provided.
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Affiliation(s)
- Yu Haowei
- Centre for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, Kuala Lumpur, Malaysia
| | - Norhayati Mahyuddin
- Centre for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, Kuala Lumpur, Malaysia
| | - Nik Nazri Bin Nik Ghazali
- Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia
| | - Zeyu Wang
- China Nuclear Power Engineering Co. Ltd, Beijing Institute of Nuclear Engineering, Beijing, China
| | - Yiqiao Liu
- Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia
| | - Song Pan
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
- Key Laboratory for Comprehensive Energy Saving of Cold Regions Architecture of Ministry of Education, Jilin Jianzhu University, Changchun, PR China
| | - Irfan Anjum Badruddin
- Mechanical Engineering Department, College of Engineering, King Khalid University, Abha, Saudi Arabia
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Niu Y, Wang F, Luo D, Shu Z, Huang J, Zhang Y, Liu C, Qian H. Vertical transmission of infectious aerosols through building toilet drainage system: An experimental study. Environ Pollut 2024; 343:123284. [PMID: 38163630 DOI: 10.1016/j.envpol.2023.123284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 12/23/2023] [Accepted: 12/30/2023] [Indexed: 01/03/2024]
Abstract
The building's toilet drainage system has been identified as a potential route for the transmission of SARS-CoV-2 during outbreaks. This study employed agar-fluorescein sodium semi-solid as trace particles to investigate the possibility of vertical transmission of the SARS-CoV-2 in drainage system. In both scenarios, where floor drains were all properly sealed or dried out, simulated faeces containing fluorescein sodium were flushed into the toilet bowl. Air sampling was conducted in each restroom, and differential pressure measurements at the floor drain locations were taken. The experimental results showed that when all floor drains were properly sealed, the differential pressure at each floor drain was 0. The fluorescein sodium-traced aerosol did not transmit through the drainage system to various floors, which significantly reduced the risk of infection for users through this route. However, when all floor drains dried out, toilet users above the neutral pressure layer (NPL) were at a high risk of virus infection. Due to the increasing maximum negative pressure at the floor drain above the NPL with ascending floor levels, users on each floor above the NPL faced an elevated infection risk in restrooms. Specifically, users on the top floor were exposed to infectious aerosols roughly 1.6 times that of the first floor above the NPL. Conversely, owing to the increasing maximum positive pressure at the floor drain below the NPL with descending floor levels, users below the NPL experienced a comparatively lower infection risk. This finding has important implications for understanding the vertical transmission dynamics of SARS-CoV-2 in residential or public building and can inform the development of effective control measures.
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Affiliation(s)
- Yuanyuan Niu
- School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Fang Wang
- School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Danting Luo
- School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Zhiyong Shu
- School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Jiayu Huang
- School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Yongpeng Zhang
- School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Cong Liu
- School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, 210096, China.
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Braggion A, Dugerdil A, Wilson O, Hovagemyan F, Flahault A. Indoor Air Quality and COVID-19: A Scoping Review. Public Health Rev 2024; 44:1605803. [PMID: 38273885 PMCID: PMC10810127 DOI: 10.3389/phrs.2023.1605803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 11/09/2023] [Indexed: 01/27/2024] Open
Abstract
Objectives: The COVID-19 pandemic has been a major public health concern for the past 3 years. Scientific evidence on the relationship between SARS-CoV-2 infection and indoor air quality still needs to be demonstrated. This scoping review aims to study the association between air quality indoors and COVID-19. Methods: A scoping review analyzing the association between indoor air quality and epidemiological outcomes was conducted. Papers published between 1 January 2020 and 31 October 2022 were included. Hospital settings were excluded from the study. Results: Eight relevant articles met the inclusion criteria. Indoor settings included workplaces, schools, restaurants, and public transport. Types of ventilation used to improve indoor air quality were dilution methods (opening windows) and mechanical systems with or without filtration or purifier. CO2 sensors were employed in one study. All the studies showed a positive association between indoor air quality and its improvement and epidemiological indicators. Conclusion: The findings of this scoping review indicate that indoor air quality, which can be improved with ventilation methods, may reduce the risk of developing COVID-19. Ventilation could thus be viewed as a possible effective mitigating method.
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Affiliation(s)
- Axelle Braggion
- Institut de Santé Globale, Faculté de Médecine, Université de Genève, Geneva, Switzerland
| | - Adeline Dugerdil
- Institut de Santé Globale, Faculté de Médecine, Université de Genève, Geneva, Switzerland
| | - Olwen Wilson
- Institut de Santé Globale, Faculté de Médecine, Université de Genève, Geneva, Switzerland
- School of Public Policy, London School of Economics, London, United Kingdom
| | - Francesca Hovagemyan
- Institut de Santé Globale, Faculté de Médecine, Université de Genève, Geneva, Switzerland
| | - Antoine Flahault
- Institut de Santé Globale, Faculté de Médecine, Université de Genève, Geneva, Switzerland
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Kuribayashi ST, Yamagishi T, Suzuki N, Asari G, Abo R, Yamamoto H, Yasutomi K, Ohara T, Tachibana Y, Shimada T, Sunagawa T. Association of a promotional campaign for local dining facilities with the occurrence of COVID-19 in Asahikawa City, Japan, in November 2021. Public Health Pract (Oxf) 2023; 6:100403. [PMID: 38099089 PMCID: PMC10719406 DOI: 10.1016/j.puhip.2023.100403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 06/08/2023] [Accepted: 06/12/2023] [Indexed: 12/17/2023] Open
Abstract
Objectives As social restrictions of COVID-19 are being eased worldwide, preventing SARS-CoV-2 transmission among staff members and customers in dining facilities is essential to continuously running business because restaurants and bars are high-risk locations for COVID-19 outbreaks. In 2021, COVID-19 outbreaks occurred at restaurants or bars in Asahikawa city, Japan two weeks after the launch of a promotional campaign for local dining facilities. We investigated this event to assess the association between the promotional campaign and the occurrence of SARS-CoV-2 infection. Study design Cohort study. Methods We assessed the association between the occurrence of COVID-19 cases in the restaurants and bars and their participation in the campaign by calculating risk ratio and 95% confidence interval. Results Cases were identified among workers or customers in 4.0% (4/101) of the participating restaurants or bars and in 1.2% (39/3257) of the non-participating restaurants or bars. The risk ratio was 3.3 (95% confidence interval 1.2-9.0). Conclusion The association between the occurrence of SARS-CoV-2 infection in the restaurants or bars and participation in the campaign is undeniable. Promotional campaigns to vitalize dining facilities should be accompanied by enhanced infection prevention measures, especially ventilation.
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Affiliation(s)
| | - Takuya Yamagishi
- Antimicrobial Resistance Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Naoki Suzuki
- Asahikawa City Public Health Office, Hokkaido, Japan
| | - Go Asari
- Asahikawa City Public Health Office, Hokkaido, Japan
| | - Rieko Abo
- Asahikawa City Public Health Office, Hokkaido, Japan
| | | | | | - Tsukasa Ohara
- Hokkaido Government Department of Health and Welfare, Hokkaido, Japan
| | - Yasuko Tachibana
- Hokkaido Government Department of Health and Welfare, Hokkaido, Japan
| | - Tomoe Shimada
- Center for Field Epidemiology Intelligence, Research, and Professional Development, National Institute of Infectious Diseases, Tokyo, Japan
| | - Tomimasa Sunagawa
- Center for Field Epidemiology Intelligence, Research, and Professional Development, National Institute of Infectious Diseases, Tokyo, Japan
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Cooper DK, Sobolik JS, Kovacevic J, Rock CM, Sajewski ET, Guest JL, Lopman BA, Jaykus LA, Leon JS. Combined Infection Control Interventions Protect Essential Food Workers from Occupational Exposures to SARS-CoV-2 in the Agricultural Environment. Appl Environ Microbiol 2023; 89:e0012823. [PMID: 37310232 PMCID: PMC10370312 DOI: 10.1128/aem.00128-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 05/22/2023] [Indexed: 06/14/2023] Open
Abstract
Essential food workers experience elevated risks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection due to prolonged occupational exposures in food production and processing areas, shared transportation (car or bus), and employer-provided shared housing. Our goal was to quantify the daily cumulative risk of SARS-CoV-2 infection for healthy susceptible produce workers and to evaluate the relative reduction in risk attributable to food industry interventions and vaccination. We simulated daily SARS-CoV-2 exposures of indoor and outdoor produce workers through six linked quantitative microbial risk assessment (QMRA) model scenarios. For each scenario, the infectious viral dose emitted by a symptomatic worker was calculated across aerosol, droplet, and fomite-mediated transmission pathways. Standard industry interventions (2-m physical distancing, handwashing, surface disinfection, universal masking, ventilation) were simulated to assess relative risk reductions from baseline risk (no interventions, 1-m distance). Implementation of industry interventions reduced an indoor worker's relative infection risk by 98.0% (0.020; 95% uncertainty interval [UI], 0.005 to 0.104) from baseline risk (1.00; 95% UI, 0.995 to 1.00) and an outdoor worker's relative infection risk by 94.5% (0.027; 95% UI, 0.013 to 0.055) from baseline risk (0.487; 95% UI, 0.257 to 0.825). Integrating these interventions with two-dose mRNA vaccinations (86 to 99% efficacy), representing a worker's protective immunity to infection, reduced the relative infection risk from baseline for indoor workers by 99.9% (0.001; 95% UI, 0.0002 to 0.005) and outdoor workers by 99.6% (0.002; 95% UI, 0.0003 to 0.005). Consistent implementation of combined industry interventions, paired with vaccination, effectively mitigates the elevated risks from occupationally acquired SARS-CoV-2 infection faced by produce workers. IMPORTANCE This is the first study to estimate the daily risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across a variety of indoor and outdoor environmental settings relevant to food workers (e.g., shared transportation [car or bus], enclosed produce processing facility and accompanying breakroom, outdoor produce harvesting field, shared housing facility) through a linked quantitative microbial risk assessment framework. Our model has demonstrated that the elevated daily SARS-CoV-2 infection risk experienced by indoor and outdoor produce workers can be reduced below 1% when vaccinations (optimal vaccine efficacy, 86 to 99%) are implemented with recommended infection control strategies (e.g., handwashing, surface disinfection, universal masking, physical distancing, and increased ventilation). Our novel findings provide scenario-specific infection risk estimates that can be utilized by food industry managers to target high-risk scenarios with effective infection mitigation strategies, which was informed through more realistic and context-driven modeling estimates of the infection risk faced by essential food workers daily. Bundled interventions, particularly if they include vaccination, yield significant reductions (>99%) in daily SARS-CoV-2 infection risk for essential food workers in enclosed and open-air environments.
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Affiliation(s)
- D. Kane Cooper
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Julia S. Sobolik
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Jovana Kovacevic
- Food Innovation Center, Oregon State University, Portland, Oregon, USA
| | - Channah M. Rock
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, USA
| | | | - Jodie L. Guest
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Ben A. Lopman
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Lee-Ann Jaykus
- Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Juan S. Leon
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
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Zhang N, Liu L, Dou Z, Liu X, Yang X, Miao D, Guo Y, Gu S, Li Y, Qian H, Wei J. Close contact behaviors of university and school students in 10 indoor environments. J Hazard Mater 2023; 458:132069. [PMID: 37463561 DOI: 10.1016/j.jhazmat.2023.132069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/24/2023] [Accepted: 07/13/2023] [Indexed: 07/20/2023]
Abstract
Close contact routes, including short-range airborne and large-droplet routes, play an important role in the transmission of SARS-CoV-2 in indoor environments. However, the exposure risk of such routes is difficult to quantify due to the lack of data on the close contact behavior of individuals. In this study, a digital wearable device, based on semi-supervised learning, was developed to automatically record human close contact behavior. We collected 337,056 s of indoor close contact of school and university students from 194.5 h of depth video recordings in 10 types of indoor environments. The correlation between aerosol exposure and close contact behaviors was then evaluated. Individuals in restaurants had the highest close contact ratio (64%), as well as the highest probability of face-to-face pattern (78%) during close contact. Accordingly, university students showed greater exposure potential in dormitories than school students in homes, however, a lower exposure was observed in classrooms and postgraduate student offices in comparison with school students in classrooms. In addition, restaurants had the highest aerosol exposure volume for both short-range inhalation and direct deposition on the facial mucosa. Thus, the classroom was established as the primary indoor environment where school students are exposed to aerosols.
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Hong Kong, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xueze Yang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Doudou Miao
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Yong Guo
- Department of Building Science, Tsinghua University, Beijing, China
| | - Silan Gu
- Thee First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China.
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Hirokawa K, Hirota J, Kawaguchi D, Masaki Y, Onita C. Investigating the epidemiological and economic effects of a third-party certification policy for restaurants with COVID-19 prevention measures. Sci Rep 2023; 13:7655. [PMID: 37169796 PMCID: PMC10173234 DOI: 10.1038/s41598-023-34498-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 05/03/2023] [Indexed: 05/13/2023] Open
Abstract
This study investigates the effects of a third-party certification policy for restaurants (including bars) that comply with indoor infection-prevention measures on COVID-19 cases and economic activities. We focus on the case of Yamanashi Prefecture in Japan, which introduced a third-party certification policy that accredits facilities, predominantly restaurants, that comply with the designated guidelines. We employ a difference-in-differences design for each of our epidemiological and economic analyses. The estimation results show that, from July 2020 to April 2021, the certification policy reduced the total number of new infection cases by approximately 45.3% (848 cases), while increasing total sales and the number of customers per restaurant by approximately 12.8% (3.21 million Japanese yen or $30,000) and 30.3% (2909 customers), respectively, compared to the non-intervention scenarios. The results suggest that a third-party certification policy can be an effective policy to mitigate the trade-off between economic activities and infection prevention during a pandemic, especially when effective vaccines are not widely available.
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Affiliation(s)
- Kazuya Hirokawa
- Graduate School of Public Policy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Jumpei Hirota
- Graduate School of Public Policy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Daiji Kawaguchi
- Graduate School of Public Policy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- RIETI, Tokyo, Japan.
- IZA, Bonn, Germany.
| | - Yusuke Masaki
- Graduate School of Public Policy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Chiaki Onita
- Graduate School of Public Policy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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Guo Y, Dou Z, Zhang N, Liu X, Su B, Li Y, Zhang Y. Student close contact behavior and COVID-19 transmission in China's classrooms. PNAS Nexus 2023; 2:pgad142. [PMID: 37228510 PMCID: PMC10205473 DOI: 10.1093/pnasnexus/pgad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 04/10/2023] [Accepted: 04/14/2023] [Indexed: 05/27/2023]
Abstract
Classrooms are high-risk indoor environments, so analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in classrooms is important for determining optimal interventions. Due to the absence of human behavior data, it is challenging to accurately determine virus exposure in classrooms. A wearable device for close contact behavior detection was developed, and we recorded >250,000 data points of close contact behaviors of students from grades 1 to 12. Combined with a survey on students' behaviors, we analyzed virus transmission in classrooms. Close contact rates for students were 37 ± 11% during classes and 48 ± 13% during breaks. Students in lower grades had higher close contact rates and virus transmission potential. The long-range airborne transmission route is dominant, accounting for 90 ± 3.6% and 75 ± 7.7% with and without mask wearing, respectively. During breaks, the short-range airborne route became more important, contributing 48 ± 3.1% in grades 1 to 9 (without wearing masks). Ventilation alone cannot always meet the demands of COVID-19 control; 30 m3/h/person is suggested as the threshold outdoor air ventilation rate in a classroom. This study provides scientific support for COVID-19 prevention and control in classrooms, and our proposed human behavior detection and analysis methods offer a powerful tool to understand virus transmission characteristics and can be employed in various indoor environments.
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Affiliation(s)
- Yong Guo
- Department of Building Science, Tsinghua University, Beijing 100084, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing 100084, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Beijing 999077, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing 100124, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing 100124, China
| | - Boni Su
- Clean Energy Research Institute, China Electric Power Planning and Engineering Institute, Beijing 100120, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR 999077, China
| | - Yinping Zhang
- Department of Building Science, Tsinghua University, Beijing 100084, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing 100084, China
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11
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Jiang Z, Deng Z, Wang X, Dong B. PANDEMIC: Occupancy driven predictive ventilation control to minimize energy consumption and infection risk. Appl Energy 2023; 334:120676. [PMID: 36714219 PMCID: PMC9867897 DOI: 10.1016/j.apenergy.2023.120676] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 05/31/2023]
Abstract
During the SARS-CoV-2 (COVID-19) pandemic, governments around the world have formulated policies requiring ventilation systems to operate at a higher outdoor fresh air flow rate for a sufficient time, which has led to a sharp increase in building energy consumption. Therefore, it is necessary to identify an energy-efficient ventilation strategy to reduce the risk of infection. In this study, we developed an occupant-number-based model predictive control (OBMPC) algorithm for building ventilation systems. First, we collected the occupancy and Heating, ventilation, and air conditioning system (HVAC) data from March to July 2021. Then, four different models (Auto regression moving average-based multilayer perceptron (ARMA_MLP), Recurrent neural networks (RNN), Long short-term memory networks (LSTM), and Nonhomogeneous Markov with change points detection (NH_Markov)) were used to predict the number of room occupants from 15 min to 24 h ahead with an interval output. We found that each model could predict the number of occupants with 85 % accuracy using a one-person offset. The accuracy of 15 min of the ahead prediction could reach 95 % with a one-person offset, but none of them could track abrupt changes. The occupancy prediction results were used to calculate the ventilation demand using the Wells-Riley equation, and the upper bound can maintain an infection risk lower than 2 % for 93 % of the day. This OBMPC model could reduce the coil load by 52.44 % and shift the peak load by 3 h up to 5 kW compared with 24 × 7 h full outdoor air (OA) system when people wear masks in the space. The occupancy prediction uncertainty could cause a 9 % to 26 % difference in demand ventilation, a 0.3 °C to 2.4 °C difference in zone temperature, a 28.5 % to 44.5 % difference in outdoor airflow rate, and a 10.7 % to 28.2 % difference in coil load.
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Affiliation(s)
- Zixin Jiang
- Department of Mechanical & Aerospace Engineering, Syracuse University, Syracuse, NY 13244, United States
- Built Environment Science and Technology (BEST) Lab, Syracuse University, Syracuse, NY 13244, United States
| | - Zhipeng Deng
- Department of Mechanical & Aerospace Engineering, Syracuse University, Syracuse, NY 13244, United States
- Built Environment Science and Technology (BEST) Lab, Syracuse University, Syracuse, NY 13244, United States
| | - Xuezheng Wang
- Department of Mechanical & Aerospace Engineering, Syracuse University, Syracuse, NY 13244, United States
- Built Environment Science and Technology (BEST) Lab, Syracuse University, Syracuse, NY 13244, United States
| | - Bing Dong
- Department of Mechanical & Aerospace Engineering, Syracuse University, Syracuse, NY 13244, United States
- Built Environment Science and Technology (BEST) Lab, Syracuse University, Syracuse, NY 13244, United States
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12
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Zhang N, Hu T, Shang S, Zhang S, Jia W, Chen J, Zhang Z, Su B, Wang Z, Cheng R, Li Y. Local travel behaviour under continuing COVID-19 waves- A proxy for pandemic fatigue? Transp Res Interdiscip Perspect 2023; 18:100757. [PMID: 36694823 PMCID: PMC9850857 DOI: 10.1016/j.trip.2023.100757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 01/06/2023] [Accepted: 01/14/2023] [Indexed: 06/11/2023]
Abstract
COVID-19 continues to threaten the world. Relaxing local travel behaviours on preventing the spread of COVID-19, may increase the infection risk in subsequent waves of SARS-CoV-2 transmission. In this study, we analysed changes in the travel behaviour of different population groups (adult, child, student, elderly) during four pandemic waves in Hong Kong before January 2021, by 4-billion second-by-second smartcard records of subway. A significant continuous relaxation in human travel behaviour was observed during the four waves of SARS-CoV-2 transmission. Residents sharply reduced their local travel by 51.9%, 50.1%, 27.6%, and 20.5% from the first to fourth pandemic waves, respectively. The population flow in residential areas, workplaces, schools, shopping areas, amusement areas and border areas, decreased on average by 30.3%, 33.5%, 41.9%, 58.1%, 85.4% and 99.6%, respectively, during the pandemic weeks. We also found that many other cities around the world experienced a similar relaxation trend in local travel behaviour, by comparing traffic congestion data during the pandemic with data from the same period in 2019. The quantitative pandemic fatigue in local travel behaviour could help governments partially predicting personal protective behaviours, and thus to suggest more accurate interventions during subsequent waves, especially for highly infectious virus variants such as Omicron.
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Tingrui Hu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Shujia Shang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Shiyao Zhang
- The Sifakis Research Institute for Trustworthy Autonomous Systems, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wei Jia
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Jinhang Chen
- Faculty of Information Technology, Beijing University of Technology, Beijing, China
| | - Zixuan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Zhenyu Wang
- College of Economics and Management, Beijing University of Technology, Beijing, China
| | - Reynold Cheng
- Department of Computer Science, The University of Hong Kong, Hong Kong SAR, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
- School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
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13
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Chen W, Liu L, Zhang N, Hang J, Li Y. Conversational head movement decreases close-contact exposure to expired respiratory droplets. J Hazard Mater 2023; 444:130406. [PMID: 36417778 DOI: 10.1016/j.jhazmat.2022.130406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/01/2022] [Accepted: 11/13/2022] [Indexed: 06/16/2023]
Abstract
People constantly move their heads during conversation, as such movement is an important non-verbal mode of communication. Head movement alters the direction of people's expired air flow, therefore affecting their conversational partners' level of exposure. Nevertheless, there is a lack of understanding of the mechanism whereby head movement affects people's exposure. In this study, a dynamic meshing method in computational fluid dynamics was used to simulate the head movement of a human-shaped thermal manikin. Droplets were released during the oral expiration periods of the source manikin, during which it was either motionless, was shaking its head or was nodding its head, while the head of a face-to-face target manikin remained motionless. The results indicate that the target manikin had a high level of exposure to respiratory droplets when the source manikin was motionless, whereas the target manikin's level of exposure was significantly reduced when the source manikin was shaking or nodding its head. The source manikin had the highest level of self-exposure when it was nodding its head and the lowest level of self-exposure when its head was motionless. People's level of exposure during close contact is highly variable, highlighting the need for further investigations in more realistic conversational scenarios.
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Affiliation(s)
- Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Li Liu
- Department of Building Science, Tsinghua University, Beijing 100084, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China; Faculty of Architecture, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
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14
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Han L, Lin Z, Tang M, Liu Y, Guan S. Impact of human contact patterns on epidemic spreading in time-varying networks. Phys Rev E 2023; 107:024312. [PMID: 36932475 DOI: 10.1103/physreve.107.024312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Accepted: 02/06/2023] [Indexed: 03/19/2023]
Abstract
Human contact behaviors involve both dormant and active processes. The dormant (active) process goes from the disappearance (creation) to the creation (disappearance) of an edge. The dormant (active) time is the elapsed time since the edge became dormant (active). Many empirical studies have revealed that dormant and active times in human contact behaviors tend to show a long-tailed distribution. Previous researches focused on the impact of the dormant process on spreading dynamics. However, the epidemic spreading happens on the active process. This raises the question of how the active process affects epidemic spreading in complex networks. Here, we propose a novel time-varying network model in which the distributions of both the dormant time and active time of edges are adjustable. We develop a pairwise approximation method to describe the spreading dynamical processes in the time-varying networks. Through extensive numerical simulations, we find that the epidemic threshold is proportional to the mean dormant time and inversely proportional to the mean active time. The attack rate decreases with the increase of mean dormant time and increases with the increase of mean active time. It is worth noting that the epidemic threshold and the attack rate (e.g., the infected density in the steady state) are independent of the heterogeneities of the dormant time distribution and the active time distribution. Increasing the heterogeneity of the dormant time distribution accelerates epidemic spreading while increasing the heterogeneity of the active time distribution slows it down.
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Affiliation(s)
- Lilei Han
- School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China
| | - Zhaohua Lin
- Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, China
| | - Ming Tang
- School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China
- Shanghai Key Laboratory of Multidimensional Information Processing, East China Normal University, Shanghai 200241, China
| | - Ying Liu
- School of Computer Science, Southwest Petroleum University, Chengdu 610500, China
| | - Shuguang Guan
- School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China
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15
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Tan K, Gao B, Yang CH, Johnson EL, Hsu MC, Passalacqua A, Krishnamurthy A, Ganapathysubramanian B. A computational framework for transmission risk assessment of aerosolized particles in classrooms. Eng Comput 2023:1-22. [PMID: 36742376 PMCID: PMC9884603 DOI: 10.1007/s00366-022-01773-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 11/28/2022] [Indexed: 06/18/2023]
Abstract
Infectious airborne diseases like the recent COVID-19 pandemic render confined spaces high-risk areas. However, in-person activities like teaching in classroom settings and government services are often expected to continue or restart quickly. It becomes important to evaluate the risk of airborne disease transmission while accounting for the physical presence of humans, furniture, and electronic equipment, as well as ventilation. Here, we present a computational framework and study based on detailed flow physics simulations that allow straightforward evaluation of various seating and operating scenarios to identify risk factors and assess the effectiveness of various mitigation strategies. These scenarios include seating arrangement changes, presence/absence of computer screens, ventilation rate changes, and presence/absence of mask-wearing. This approach democratizes risk assessment by automating a key bottleneck in simulation-based analysis-creating an adequately refined mesh around multiple complex geometries. Not surprisingly, we find that wearing masks (with at least 74% inward protection efficiency) significantly reduced transmission risk against unmasked and infected individuals. While the use of face masks is known to reduce the risk of transmission, we perform a systematic computational study of the transmission risk due to variations in room occupancy, seating layout and air change rates. In addition, our findings on the efficacy of face masks further support use of face masks. The availability of such an analysis approach will allow education administrators, government officials (courthouses, police stations), and hospital administrators to make informed decisions on seating arrangements and operating procedures. Supplementary Information The online version contains supplementary material available at 10.1007/s00366-022-01773-9.
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Affiliation(s)
- Kendrick Tan
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore, 138632 Singapore
| | - Boshun Gao
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
| | - Cheng-Hau Yang
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
| | - Emily L. Johnson
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Ming-Chen Hsu
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
| | - Alberto Passalacqua
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 USA
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16
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Cox J, Christensen B, Burton N, Dunn KH, Finnegan M, Ruess A, Estill C. Transmission of SARS-CoV-2 in the workplace: Key findings from a rapid review of the literature. Aerosol Sci Technol 2023; 57:233-254. [PMID: 37213938 PMCID: PMC10193509 DOI: 10.1080/02786826.2023.2166394] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 12/27/2022] [Indexed: 05/23/2023]
Abstract
At the beginning of the COVID-19 pandemic, the primary route of transmission of the SARS-CoV-2 virus was not well understood. Research gathered from other respiratory infectious diseases, including other coronaviruses, was the basis for the initial perceptions for transmission of SARS-CoV-2. To better understand transmission of SARS-CoV-2, a rapid literature review was conducted from literature generated March 19, 2020, through September 23, 2021. 18,616 unique results were identified from literature databases and screened. Of these, 279 key articles were reviewed and abstracted covering critical topics such as environmental/workplace monitoring, sampling and analytical method evaluation, and the ability of the virus to remain intact and infectious during sampling. This paper describes the results of the rapid literature review, which evaluated pathways that contribute to transmission as well as the strengths and limitations of current sampling approaches. This review also evaluates how different factors, including environmental conditions and surface characteristics, could impact the transmission potential of SARS-CoV-2. A continual rapid review in the midst of a pandemic proved particularly useful for quickly understanding the transmission parameters of the virus and enabled us to comprehensively assess literature, respond to workplace questions, and evaluate our understanding as the science evolved. Air and surface sampling with the accompanying analytical methods were not generally effective in recovering SARS-CoV-2 viable virus or RNA in many likely contaminated environments. In light of these findings, the development of validated sampling and analysis methods is critical for determining worker exposure to SARS-CoV-2 and to assess the impact of mitigation efforts.
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Affiliation(s)
- Jennie Cox
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - Brian Christensen
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - Nancy Burton
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - Kevin H. Dunn
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | | | - Ana Ruess
- Gryphon Scientific, Takoma Park, MD, USA
| | - Cherie Estill
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
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17
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Mazoteras-Pardo V, Losa-Iglesias ME, Casado-Hernández I, Calvo-Lobo C, Morales-Ponce Á, Medrano-Soriano A, Coco-Villanueva S, Becerro-de-Bengoa-Vallejo R. Indoor air quality in a training centre used for sports practice. PeerJ 2023; 11:e15298. [PMID: 37151296 PMCID: PMC10158773 DOI: 10.7717/peerj.15298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 04/04/2023] [Indexed: 05/09/2023] Open
Abstract
Background One of the measures for controlling the coronavirus disease 2019 (COVID-19) pandemic was the mass closure of gyms. This measure leads us to determine the differences between indoor and outdoor air quality. That is why the objective of this study was to analyse the indoor air quality of a sports centre catering to small groups and rehabilitation. Methods The study was conducted in a single training centre, where 26 measurements were taken in two spaces (indoors and outdoors). The air quality index, temperature, relative humidity, total volatile compounds, carbon monoxide, ozone, formaldehyde, carbon dioxide, and particulate matter were measured indoors and outdoors using the same protocol and equipment. These measurements were taken twice, once in the morning and once in the afternoon, with all measurements made at the same time, 10 am and 6 pm, respectively. Additionally, four determinations of each variable were collected during each shift, and the number of people who had trained in the room and the number of trainers were counted. Results In the different variables analysed, the results show that CO2 and RH levels are higher indoors than outdoors in both measurement shifts. Temperatures are higher outside than inside and, in the evening, than in the morning. TVOC, AQI and PM show less variation, although they are higher outdoors in the morning. CO is highest indoors. HCHO levels are almost negligible and do not vary significantly, except for a slight increase in the afternoon outside. Ozone levels are not significant. All the variables showed practically perfect reliability in all the measurements, except for ozone measured outside in the morning. On the other hand, the variables exhibit variations between indoors and outdoors during the morning and afternoon, except for the three types of PM. Also, the data show that all the main variables measured inside the sports training centre are similar between morning and afternoon. However, outside, temperature, relative humidity and HCHO levels show significant differences between morning and afternoon while no differences are observed for the other variables. Conclusion The indoor air quality of the training centre assessed was good and met current regulations; some of its components even exhibited better levels than fresh air. This article is the first to measure indoor air quality in a sports training centre catering to rehabilitation and small groups.
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Affiliation(s)
- Victoria Mazoteras-Pardo
- Department of Nursing, Physiotherapy and Occupational Therapy, Faculty of Physiotherapy and Nursing of Toledo, Toledo, Spain
| | - Marta Elena Losa-Iglesias
- Department of Nursing, Faculty of Health Sciences. Universidad Rey Juan Carlos de Madrid, Madrid, Spain
| | - Israel Casado-Hernández
- Department of Nursing, Faculty of Nursing, Physiotherapy and Podiatry, Universidad Complutense de Madrid, Madrid, Spain
| | - César Calvo-Lobo
- Department of Nursing, Faculty of Nursing, Physiotherapy and Podiatry, Universidad Complutense de Madrid, Madrid, Spain
| | - Ángel Morales-Ponce
- Department of Nursing, Faculty of Nursing, Physiotherapy and Podiatry, Universidad Complutense de Madrid, Madrid, Spain
| | - Alfredo Medrano-Soriano
- Department of Nursing, Faculty of Nursing, Physiotherapy and Podiatry, Universidad Complutense de Madrid, Madrid, Spain
| | - Sergio Coco-Villanueva
- Department of Nursing, Faculty of Nursing, Physiotherapy and Podiatry, Universidad Complutense de Madrid, Madrid, Spain
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18
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Chen W, Liu L, Hang J, Li Y. Predominance of inhalation route in short-range transmission of respiratory viruses: Investigation based on computational fluid dynamics. Build Simul 2022; 16:765-780. [PMID: 36575690 PMCID: PMC9782262 DOI: 10.1007/s12273-022-0968-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 11/19/2022] [Accepted: 11/25/2022] [Indexed: 05/28/2023]
Abstract
During the Coronavirus disease 2019 pandemic, short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission. However, the roles played by the inhalation and large droplet routes cannot be distinguished in practice. A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections. In the current study, short-range exposure was analyzed via computational fluid dynamics (CFD) simulations using a discrete phase model. Detailed facial membranes, including eyes, nostrils, and a mouth, were considered. In CFD simulations, there is no need for a spherical approximation of the human head for estimating deposition nor the "anisokinetic aerosol sampling" approximation for estimating inhalation in the analytical model. We considered two scenarios (with two spheres [Scenario 1] and two human manikins [Scenario 2]), source-target distances of 0.2 to 2 m, and droplet diameters of 3 to 1,500 µm. The overall CFD exposure results agree well with data previously obtained from a simple analytical model. The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50 µm during talking and coughing. A critical droplet size of 87.5 µm was found to differentiate droplet behaviors. The number of droplets deposited on the target head exceeded those exposed to facial membranes, which implies a risk of exposure through the immediate surface route over a short range. Electronic Supplementary Material ESM the Supplementary Materials are available in the online version of this article at 10.1007/s12273-022-0968-y.
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Affiliation(s)
- Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Li Liu
- Department of Building Science, Tsinghua University, Beijing, 100084 China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082 China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
- Faculty of Architecture, The University of Hong Kong, Pokfulam Road, Hong Kong, China
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19
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Aikebaier S, Song Y, Li M, Liu J. Exploring the Impact and Prevention of Epidemics from a New Perspective: COVID-19 Transmission through Express Boxes. Int J Environ Res Public Health 2022; 19:16884. [PMID: 36554764 PMCID: PMC9778959 DOI: 10.3390/ijerph192416884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/06/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
The number of express boxes worldwide exceeded 170 billion in 2021, and, from several regions in China, tested positive. Therefore, it is important to study the transmission of viruses through express boxes. In this paper, we establish a model of express box virus transmission based on comprehensive consideration of environmental factors, such as temperature, disinfection, humidity, virus release intensity, and volume of vehicle, to study the transmission of express box virus, and explore the spatial and geographic spread variation of express box viruses in China. Several important findings emerged from the study, including: (1) Disinfection can prolong the spread of viruses in the express box for ≥21 h; (2) For every 1 °C rise in temperature, the infected time can be prolonged by ≥1.2 h, and for every 10% rise in relative humidity, the virus transmission time can be prolonged by ≥1.32 h; (3) In an environment suitable for virus transmission, when loaded with 1000, 2000, 4000 express boxes, areas where the express delivery time exceeds 22.56, 18, 14.64 h will face the risk of all the boxes in the carriage being infected. These findings could help public health departments prevent the risk of virus transmission from express boxes.
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Affiliation(s)
- Saierdaer Aikebaier
- China Emergency Management Research Center, Wuhan University of Technology, Wuhan 430070, China
- Hubei Collaborative Innovation Center of Safety Early Warning and Emergency Response Technology, Wuhan 430070, China
| | - Yinghua Song
- China Emergency Management Research Center, Wuhan University of Technology, Wuhan 430070, China
- Hubei Collaborative Innovation Center of Safety Early Warning and Emergency Response Technology, Wuhan 430070, China
| | - Moxiao Li
- China Emergency Management Research Center, Wuhan University of Technology, Wuhan 430070, China
- Hubei Collaborative Innovation Center of Safety Early Warning and Emergency Response Technology, Wuhan 430070, China
| | - Jiexin Liu
- China Emergency Management Research Center, Wuhan University of Technology, Wuhan 430070, China
- Hubei Collaborative Innovation Center of Safety Early Warning and Emergency Response Technology, Wuhan 430070, China
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20
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Oksanen L, Auvinen M, Kuula J, Malmgren R, Romantschuk M, Hyvärinen A, Laitinen S, Maunula L, Sanmark E, Geneid A, Sofieva S, Salokas J, Veskiväli H, Sironen T, Grönholm T, Hellsten A, Atanasova N. Combining Phi6 as a surrogate virus and computational large-eddy simulations to study airborne transmission of SARS-CoV-2 in a restaurant. Indoor Air 2022; 32:e13165. [PMID: 36437671 PMCID: PMC10100099 DOI: 10.1111/ina.13165] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 09/30/2022] [Accepted: 10/08/2022] [Indexed: 05/18/2023]
Abstract
COVID-19 has highlighted the need for indoor risk-reduction strategies. Our aim is to provide information about the virus dispersion and attempts to reduce the infection risk. Indoor transmission was studied simulating a dining situation in a restaurant. Aerosolized Phi6 viruses were detected with several methods. The aerosol dispersion was modeled by using the Large-Eddy Simulation (LES) technique. Three risk-reduction strategies were studied: (1) augmenting ventilation with air purifiers, (2) spatial partitioning with dividers, and (3) combination of 1 and 2. In all simulations infectious viruses were detected throughout the space proving the existence long-distance aerosol transmission indoors. Experimental cumulative virus numbers and LES dispersion results were qualitatively similar. The LES results were further utilized to derive the evolution of infection probability. Air purifiers augmenting the effective ventilation rate by 65% reduced the spatially averaged infection probability by 30%-32%. This relative reduction manifests with approximately 15 min lag as aerosol dispersion only gradually reaches the purifier units. Both viral findings and LES results confirm that spatial partitioning has a negligible effect on the mean infection-probability indoors, but may affect the local levels adversely. Exploitation of high-resolution LES jointly with microbiological measurements enables an informative interpretation of the experimental results and facilitates a more complete risk assessment.
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Affiliation(s)
- Lotta Oksanen
- Department of Otorhinolaryngology and Phoniatrics – Head and Neck SurgeryHelsinki University HospitalHelsinkiFinland
- Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | | | - Joel Kuula
- Finnish Meteorological InstituteHelsinkiFinland
| | - Rasmus Malmgren
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
| | - Martin Romantschuk
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiLahtiFinland
| | | | | | - Leena Maunula
- Faculty of Veterinary Medicine, Food Hygiene and Environmental HealthUniversity of HelsinkiHelsinkiFinland
| | - Enni Sanmark
- Department of Otorhinolaryngology and Phoniatrics – Head and Neck SurgeryHelsinki University HospitalHelsinkiFinland
- Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Ahmed Geneid
- Department of Otorhinolaryngology and Phoniatrics – Head and Neck SurgeryHelsinki University HospitalHelsinkiFinland
- Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Svetlana Sofieva
- Finnish Meteorological InstituteHelsinkiFinland
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
| | - Julija Salokas
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
| | - Helin Veskiväli
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
| | - Tarja Sironen
- Department of Virology, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
- Department of Veterinary Biosciences, Faculty of Veterinary MedicineUniversity of HelsinkiHelsinkiFinland
| | | | | | - Nina Atanasova
- Finnish Meteorological InstituteHelsinkiFinland
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
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21
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Shobako N. Lessons from the health policies for children during the pandemic in Japan. Front Public Health 2022; 10:1015955. [PMID: 36339184 PMCID: PMC9628751 DOI: 10.3389/fpubh.2022.1015955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 09/21/2022] [Indexed: 01/28/2023] Open
Abstract
It is everyone's desire to seek the sound growth of children through food education and there is a critical need for fostering an environment for this purpose. Health policies are important for this support. To the present, the Japanese society has been greatly disrupted by COVID-19 pandemic. "Stay at home", "mokusyoku (silent eating)", and mask wearing were encouraged in nationwide campaigns as public health measures to combat COVID-19. There are some papers reporting negative effects of "stay at home" and lockdowns such as weight gain, decrease in physical activities and change in eating habits. In Japan, while benefits and advantages of food education during mealtime were previously well studied, the "mokusyoku" rule may directly run counter to this food education. Moreover, there are several reports showing that nutrients might contribute to prevention of infectious diseases. Japanese children were also encouraged to wear masks all day long. The results of the clinical research, especially randomized control trials, show limited protective effect of masks. On the other hand, negative outcomes of the masks were reported in various scenes. This review focuses on these topics and arousing reconsideration for a better environment for children.
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22
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Marinov GK, Mladenov M, Rangachev A, Alexiev I. SARS-CoV-2 reinfections during the first three major COVID-19 waves in Bulgaria. PLoS One 2022; 17:e0274509. [PMID: 36084070 PMCID: PMC9462809 DOI: 10.1371/journal.pone.0274509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 08/30/2022] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND The COVID-19 pandemic has had a devastating impact on the world over the past two years (2020-2021). One of the key questions about its future trajectory is the protection from subsequent infections and disease conferred by a previous infection, as the SARS-CoV-2 virus belongs to the coronaviruses, a group of viruses the members of which are known for their ability to reinfect convalescent individuals. Bulgaria, with high rates of previous infections combined with low vaccination rates and an elderly population, presents a somewhat unique context to study this question. METHODS We use detailed governmental data on registered COVID-19 cases to evaluate the incidence and outcomes of COVID-19 reinfections in Bulgaria in the period between March 2020 and early December 2021. RESULTS For the period analyzed, a total of 4,106 cases of individuals infected more than once were observed, including 31 cases of three infections and one of four infections. The number of reinfections increased dramatically during the Delta variant-driven wave of the pandemic towards the end of 2021. We observe a moderate reduction of severe outcomes (hospitalization and death) in reinfections relative to primary infections, and a more substantial reduction of severe outcomes in breakthrough infections in vaccinated individuals. CONCLUSIONS In the available datasets from Bulgaria, prior infection appears to provide some protection from severe outcomes, but to a lower degree than the reduction in severity of breakthrough infections in the vaccinated compared to primary infections in the unvaccinated.
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Affiliation(s)
- Georgi K. Marinov
- Department of Genetics, Stanford University, Stanford, CA, United States of America
| | | | - Antoni Rangachev
- Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, Sofia, Bulgaria
- International Center for Mathematical Sciences-Sofia, Sofia, Bulgaria
| | - Ivailo Alexiev
- National Center of Infectious and Parasitic Diseases, Sofia, Bulgaria
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Jin T, Chen X, Nishio M, Zhuang L, Shiomi H, Tonosaki Y, Yokohata R, King MF, Kang M, Fujii K, Zhang N. Interventions to prevent surface transmission of an infectious virus based on real human touch behavior: a case study of the norovirus. Int J Infect Dis 2022; 122:83-92. [PMID: 35649497 PMCID: PMC9148625 DOI: 10.1016/j.ijid.2022.05.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/17/2022] [Accepted: 05/19/2022] [Indexed: 01/25/2023] Open
Abstract
OBJECTIVES Infectious viruses (e.g., SARS-CoV-2, norovirus) can transmit through surfaces. Norovirus has infected millions of individuals annually. Interventions on norovirus transmission in high-risk indoor environment are important. METHODS This study focused on a restaurant in Guangzhou, China. More than 41,000 touches by both diners and staff members were collected using video cameras. A surface transmission model was developed and combined with these real human touch behaviors to analyze the effectiveness of different norovirus prevention strategies. RESULTS When the virus carrier was a diner, the virus intake fraction of diners in the same table was the highest. Increasing the touch frequency on personal private surfaces would reduce the virus exposure. The virus intake fraction was reduced by 18.4% on average if public surfaces were not touched. Optimization on surface materials could reduce the virus intake fraction by 86.6%. Additionally, disinfecting tablecloths, clothes of diners, and chairs were the three most effective surface disinfection strategies. CONCLUSION Controlling human touch behavior (e.g., reducing the self-touches on mucous membranes) is more effective than surface disinfection in controlling norovirus transmission, but surface disinfection cannot be ignored because human behavior is difficult to be controlled.
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Affiliation(s)
- Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xuguang Chen
- Guangdong Provincial Center for Disease Control and Prevention, Guangdong province, China
| | - Masaya Nishio
- R&D-Safety Science, Kao Corporation, Japan,R&D-Strategy, Kao Corporation, Japan
| | - Linan Zhuang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Hiroyuki Shiomi
- R&D-Processing Development Research Laboratories, Kao Corporation, Japan
| | - Yosuke Tonosaki
- R&D-Processing Development Research Laboratories, Kao Corporation, Japan
| | | | | | - Min Kang
- Guangdong Provincial Center for Disease Control and Prevention, Guangdong province, China
| | - Kenkichi Fujii
- R&D-Safety Science, Kao Corporation, Japan,R&D-Strategy, Kao Corporation, Japan
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China,Corresponding author: Nan Zhang, Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Room 204, Pingleyuan 100, Chaoyang District, Beijing, China, Telephone: +86 18210064566
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24
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Liu X, Dou Z, Wang L, Su B, Jin T, Guo Y, Wei J, Zhang N. Close contact behavior-based COVID-19 transmission and interventions in a subway system. J Hazard Mater 2022; 436:129233. [PMID: 35739753 PMCID: PMC9132379 DOI: 10.1016/j.jhazmat.2022.129233] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 05/21/2022] [Accepted: 05/23/2022] [Indexed: 05/29/2023]
Abstract
During COVID-19 pandemic, analysis on virus exposure and intervention efficiency in public transports based on real passenger's close contact behaviors is critical to curb infectious disease transmission. A monitoring device was developed to gather a total of 145,821 close contact data in subways based on semi-supervision learning. A virus transmission model considering both short- and long-range inhalation and deposition was established to calculate the virus exposure. During rush-hour, short-range inhalation exposure is 3.2 times higher than deposition exposure and 7.5 times higher than long-range inhalation exposure of all passengers in the subway. The close contact rate was 56.1 % and the average interpersonal distance was 0.8 m. Face-to-back was the main pattern during close contact. Comparing with random distribution, if all passengers stand facing in the same direction, personal virus exposure through inhalation (deposition) can be reduced by 74.1 % (98.5 %). If the talk rate was decreased from 20 % to 5 %, the inhalation (deposition) exposure can be reduced by 69.3 % (73.8 %). In addition, we found that virus exposure could be reduced by 82.0 % if all passengers wear surgical masks. This study provides scientific support for COVID-19 prevention and control in subways based on real human close contact behaviors.
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Affiliation(s)
- Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Hong Kong, China
| | - Lei Wang
- Institute of Refrigeration and Cryogenics/Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Yong Guo
- Department of Building Science, Tsinghua University, Beijing, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics/Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China.
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Cheng VCC, Wong SC, Au AKW, Zhang C, Chen JHK, So SYC, Li X, Wang Q, Lu KK, Lung DC, Chuang VWM, Schuldenfrei E, Siu GKH, To KKW, Li Y, Yuen KY. Explosive outbreak of SARS-CoV-2 Omicron variant is associated with vertical transmission in high-rise residential buildings in Hong Kong. Build Environ 2022; 221:109323. [PMID: 35765578 PMCID: PMC9225940 DOI: 10.1016/j.buildenv.2022.109323] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 06/14/2022] [Accepted: 06/16/2022] [Indexed: 05/12/2023]
Abstract
The phenomenon of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in high-rise residential buildings (HRRBs) is unique in our densely populated cosmopolitan city. The compulsory testing of a whole building under the scheme of restriction-testing declaration (RTD) during the fourth wave (non-Omicron variant) and fifth wave (mostly Omicron variant) of COVID-19 outbreak in Hong Kong allowed us to study the prevalence of this phenomenon, which may represent a form of airborne transmission. From 23 January 2021 to 24 March 2022, 25,450 (5.8%) of 436,397 residents from 223 (63.0%) of 354 HRRBs under RTD were test-positive for SARS-CoV-2. Using the clustering of cases among vertically aligned flats with shared drainage stack and lightwell as a surrogate marker of vertical transmission, the number of vertically aligned flats with positive COVID-19 cases was significantly higher in the fifth wave compared with the fourth wave (14.2%, 6471/45,531 vs 0.24%, 3/1272; p < 0.001; or 2212 vs 1 per-million-flats; p < 0.001). Excluding 22,801 residents from 38 HRRBs who were tested negative outside the 12-week periods selected in fourth and fifth waves, the positive rate among residents was significantly higher among residents during the fifth wave than the fourth wave (6.5%, 25,434/389,700 vs 0.07%, 16/23,896; p < 0.001). Within the flats with COVID-19 cases, the proportion of vertically aligned flats was also significantly higher in the fifth wave than in the fourth wave (95.6%, 6471/6766 vs 30.0%, 3/10, p < 0.001). The proportion of HRRBs with COVID-19 cases was significantly higher during the corresponding 12-week period chosen for comparison (78.2%, 219/280 vs 11.1%, 4/36; p < 0.001). Whole-genome phylogenetic analysis of 332 viral genomes showed that Omicron BA.2 was the predominant strain, supporting the high transmissibility of BA.2 by airborne excreta-aerosol route in HRRBs of Hong Kong.
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Affiliation(s)
- Vincent Chi-Chung Cheng
- Infection Control Team, Queen Mary Hospital, Hong Kong West Cluster, Hong Kong Special Administrative Region, China
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
| | - Shuk-Ching Wong
- Infection Control Team, Queen Mary Hospital, Hong Kong West Cluster, Hong Kong Special Administrative Region, China
| | - Albert Ka-Wing Au
- Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region, China
| | - Cheng Zhang
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Jonathan Hon-Kwan Chen
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
| | - Simon Yung-Chun So
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
| | - Xin Li
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Qun Wang
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Kelvin Keru Lu
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region, China
| | - David Christopher Lung
- Department of Pathology, Queen Elizabeth Hospital, Hong Kong Special Administrative Region, China
| | - Vivien Wai-Man Chuang
- Quality & Safety Division, Hospital Authority, Hong Kong Special Administrative Region, China
| | - Eric Schuldenfrei
- Department of Architecture, Faculty of Architecture, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Gilman Kit-Hang Siu
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region, China
| | - Kelvin Kai-Wang To
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Yuguo Li
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Kwok-Yung Yuen
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
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Zhang N, Hu T, Zhang J, Mai W, Jian M, Li J, Chen F, Zhu M, Zhuang L, Jin T, Qian H, Li Y, Kang M. Probable close contact transmission in a restaurant in China. J Infect 2022; 85:573-607. [PMID: 36057385 PMCID: PMC9428334 DOI: 10.1016/j.jinf.2022.08.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 11/26/2022]
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Luo Q, Ou C, Hang J, Luo Z, Yang H, Yang X, Zhang X, Li Y, Fan X. Role of pathogen-laden expiratory droplet dispersion and natural ventilation explaining a COVID-19 outbreak in a coach bus. Build Environ 2022; 220:109160. [PMID: 35615259 PMCID: PMC9122785 DOI: 10.1016/j.buildenv.2022.109160] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/28/2022] [Accepted: 04/30/2022] [Indexed: 05/30/2023]
Abstract
The influencing mechanism of droplet transmissions inside crowded and poorly ventilated buses on infection risks of respiratory diseases is still unclear. Based on experiments of one-infecting-seven COVID-19 outbreak with an index patient at bus rear, we conducted CFD simulations to investigate integrated effects of initial droplet diameters(tracer gas, 5 μm, 50 μm and 100 μm), natural air change rates per hour(ACH = 0.62, 2.27 and 5.66 h-1 related to bus speeds) and relative humidity(RH = 35% and 95%) on pathogen-laden droplet dispersion and infection risks. Outdoor pressure difference around bus surfaces introduces natural ventilation airflow entering from bus-rear skylight and leaving from the front one. When ACH = 0.62 h-1(idling state), the 30-min-exposure infection risk(TIR) of tracer gas is 15.3%(bus rear) - 11.1%(bus front), and decreases to 3.1%(bus rear)-1.3%(bus front) under ACH = 5.66 h-1(high bus speed).The TIR of large droplets(i.e., 100 μm/50 μm) is almost independent of ACH, with a peak value(∼3.1%) near the index patient, because over 99.5%/97.0% of droplets deposit locally due to gravity. Moreover, 5 μm droplets can disperse further with the increasing ventilation. However, TIR for 5 μm droplets at ACH = 5.66 h-1 stays relatively small for rear passengers(maximum 0.4%), and is even smaller in the bus middle and front(<0.1%). This study verifies that differing from general rooms, most 5 μm droplets deposit on the route through the long-and-narrow bus space with large-area surfaces(L∼11.4 m). Therefore, tracer gas can only simulate fine droplet with little deposition but cannot replace 5-100 μm droplet dispersion in coach buses.
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Affiliation(s)
- Qiqi Luo
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Zhiwen Luo
- School of the Built Environment, University of Reading, Reading, UK
| | - Hongyu Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Xia Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Xuelin Zhang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Xiaodan Fan
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
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28
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Jia W, Wei J, Cheng P, Wang Q, Li Y. Exposure and respiratory infection risk via the short-range airborne route. Build Environ 2022; 219:109166. [PMID: 35574565 PMCID: PMC9085449 DOI: 10.1016/j.buildenv.2022.109166] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/16/2022] [Accepted: 05/02/2022] [Indexed: 05/09/2023]
Abstract
Leading health authorities have suggested short-range airborne transmission as a major route of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, there is no simple method to assess the short-range airborne infection risk or identify its governing parameters. We proposed a short-range airborne infection risk assessment model based on the continuum model and two-stage jet model. The effects of ventilation, physical distance and activity intensity on the short-range airborne exposure were studied systematically. The results suggested that increasing physical distance and ventilation reduced short-range airborne exposure and infection risk. However, a diminishing return phenomenon was observed when the ventilation rate or physical distance was beyond a certain threshold. When the infectious quantum concentration was less than 1 quantum/L at the mouth, our newly defined threshold distance and threshold ventilation rate were independent of quantum concentration. We estimated threshold distances of 0.59, 1.1, 1.7 and 2.6 m for sedentary/passive, light, moderate and intense activities, respectively. At these distances, the threshold ventilation was estimated to be 8, 20, 43, and 83 L/s per person, respectively. The findings show that both physical distancing and adequate ventilation are essential for minimising infection risk, especially in high-intensity activity or densely populated spaces.
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Affiliation(s)
- Wei Jia
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics/Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Qun Wang
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
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Hu T, Ji Y, Fei F, Zhu M, Jin T, Xue P, Zhang N. Optimization of COVID-19 prevention and control with low building energy consumption. Build Environ 2022; 219:109233. [PMID: 35664635 PMCID: PMC9148426 DOI: 10.1016/j.buildenv.2022.109233] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 05/23/2022] [Accepted: 05/23/2022] [Indexed: 05/20/2023]
Abstract
COVID-19 is a global threat. Non-pharmaceutical interventions were commonly adopted for COVID-19 prevention and control. However, during stable periods of the pandemic, energy would be inevitably wasted if all interventions were implemented. The study aims to reduce the building energy consumption when meet the demands of epidemic prevention and control under the stable period of COVID-19. Based on the improved Wells-Riley model considering dynamic quanta generation and pulmonary ventilation rate, we established the infection risk - equivalent fresh air volume - energy consumption model to analyze the infection risk and building energy consumption during different seasons and optimized the urban building energy consumption according to the spatio-temporal population distribution. Shopping centers and restaurants contributed the most in urban energy consumption, and if they are closed during the pandemic, the total infection risk would be reduced by 25%-40% and 15%-25% respectively and the urban energy consumption would be reduced by 30%-40% and 13%-20% respectively. If people wore masks in all public indoor environments (exclude restaurants and KTV), the infection risk could be reduced by 60%-70% and the energy consumption could be reduced by 20%-60%. Gyms pose the highest risk for COVID-19 transmission. If the energy consumption kept the same with the current value, after the optimization, infection risk in winter, summer and the transition season could be reduced by 65%, 53% and 60%, respectively. After the optimization, under the condition of R t < 1, the energy consumption in winter, summer, and the transition season could be reduced by 72%, 64%, and 68% respectively.
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Affiliation(s)
- Tingrui Hu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Ying Ji
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Fan Fei
- College of Mechatronical and Electrical Engineering, Hebei Agricultural University, Hebei province, China
| | - Min Zhu
- 6th Medical Center of General Hospital of PLA, Beijing, China
| | - Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Peng Xue
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
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Abstract
OBJECTIVES To evaluate the potential for long distance airborne transmission of SARS-CoV-2 in indoor community settings and to investigate factors that might influence transmission. DESIGN Rapid systematic review and narrative synthesis. DATA SOURCES Medline, Embase, medRxiv, Arxiv, and WHO COVID-19 Research Database for studies published from 27 July 2020 to 19 January 2022; existing relevant rapid systematic review for studies published from 1 January 2020 to 27 July 2020; and citation analysis in Web of Science and Cocites. ELIGIBILITY CRITERIA FOR STUDY SELECTION Observational studies reporting on transmission events in indoor community (non-healthcare) settings in which long distance airborne transmission of SARS-CoV-2 was the most likely route. Studies such as those of household transmission where the main transmission route was likely to be close contact or fomite transmission were excluded. DATA EXTRACTION AND SYNTHESIS Data extraction was done by one reviewer and independently checked by a second reviewer. Primary outcomes were SARS-CoV-2 infections through long distance airborne transmission (>2 m) and any modifying factors. Methodological quality of included studies was rated using the quality criteria checklist, and certainty of primary outcomes was determined using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework. Narrative synthesis was themed by setting. RESULTS 22 reports relating to 18 studies were identified (methodological quality was high in three, medium in five, and low in 10); all the studies were outbreak investigations. Long distance airborne transmission was likely to have occurred for some or all transmission events in 16 studies and was unclear in two studies (GRADE: very low certainty). In the 16 studies, one or more factors plausibly increased the likelihood of long distance airborne transmission, particularly insufficient air replacement (very low certainty), directional air flow (very low certainty), and activities associated with increased emission of aerosols, such as singing or speaking loudly (very low certainty). In 13 studies, the primary cases were reported as being asymptomatic, presymptomatic, or around symptom onset at the time of transmission. Although some of the included studies were well conducted outbreak investigations, they remain at risk of bias owing to study design and do not always provide the level of detail needed to fully assess transmission routes. CONCLUSION This rapid systematic review found evidence suggesting that long distance airborne transmission of SARS-CoV-2 might occur in indoor settings such as restaurants, workplaces, and venues for choirs, and identified factors such as insufficient air replacement that probably contributed to transmission. These results strengthen the need for mitigation measures in indoor settings, particularly the use of adequate ventilation. SYSTEMATIC REVIEW REGISTRATION PROSPERO CRD42021236762.
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Affiliation(s)
- Daphne Duval
- COVID-19 Rapid Evidence Service, UK Health Security Agency, London, UK
| | - Jennifer C Palmer
- COVID-19 Rapid Evidence Service, UK Health Security Agency, London, UK
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Science, Bristol Medical School, University of Bristol, Bristol, UK
| | - Isobel Tudge
- COVID-19 Rapid Evidence Service, UK Health Security Agency, London, UK
| | | | - Emer O'Connell
- COVID-19 Advice and Guidance, UK Health Security Agency, London, UK
| | - Allan Bennett
- Biosafety, Air, and Water Microbiology Group, Research and Evaluation, UK Health Security Agency, Porton, UK
| | - Rachel Clark
- COVID-19 Rapid Evidence Service, UK Health Security Agency, London, UK
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Coleman KK, Tay DJW, Tan KS, Ong SWX, Than TS, Koh MH, Chin YQ, Nasir H, Mak TM, Chu JJH, Milton DK, Chow VTK, Tambyah PA, Chen M, Tham KW. Viral Load of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Respiratory Aerosols Emitted by Patients With Coronavirus Disease 2019 (COVID-19) While Breathing, Talking, and Singing. Clin Infect Dis 2022; 74:1722-1728. [PMID: 34358292 DOI: 10.1101/2021.07.15.21260561] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Indexed: 05/24/2023] Open
Abstract
BACKGROUND Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) superspreading events suggest that aerosols play an important role in driving the coronavirus disease 2019 (COVID-19) pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5 μm) and fine (≤5 μm) respiratory aerosols produced when breathing, talking, and singing. METHODS Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. RESULTS Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63-5821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. CONCLUSIONS Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging; whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.
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Affiliation(s)
- Kristen K Coleman
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore
| | - Douglas Jie Wen Tay
- Department of the Built Environment, National University of Singapore, Singapore
| | - Kai Sen Tan
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Sean Wei Xiang Ong
- National Centre for Infectious Diseases, Singapore
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - The Son Than
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore
- Department of the Built Environment, National University of Singapore, Singapore
| | - Ming Hui Koh
- Department of the Built Environment, National University of Singapore, Singapore
| | - Yi Qing Chin
- National Centre for Infectious Diseases, Singapore
| | - Haziq Nasir
- Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Tze Minn Mak
- National Centre for Infectious Diseases, Singapore
| | - Justin Jang Hann Chu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Donald K Milton
- Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, Maryland, USA
| | - Vincent T K Chow
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Paul Anantharajah Tambyah
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
- Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Mark Chen
- National Centre for Infectious Diseases, Singapore
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - Kwok Wai Tham
- Department of the Built Environment, National University of Singapore, Singapore
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Cheng VCC, Lung DC, Wong SC, Au AKW, Wang Q, Chen H, Xin L, Chu AWH, Ip JD, Chan WM, Tsoi HW, Tse H, Ng KHL, Kwan MYW, Chuang SK, To KKW, Li Y, Yuen KY. Outbreak investigation of airborne transmission of Omicron (B.1.1.529) - SARS-CoV-2 variant of concern in a restaurant: Implication for enhancement of indoor air dilution. J Hazard Mater 2022; 430:128504. [PMID: 35739650 PMCID: PMC8848576 DOI: 10.1016/j.jhazmat.2022.128504] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/06/2022] [Accepted: 02/13/2022] [Indexed: 05/06/2023]
Abstract
Airborne transmission of SARS-CoV-2 has been increasingly recognized in the outbreak of COVID-19, especially with the Omicron variant. We investigated an outbreak due to Omicron variant in a restaurant. Besides epidemiological and phylogenetic analyses, the secondary attack rates of customers of restaurant-related COVID-19 outbreak before (Outbreak R1) and after enhancement of indoor air dilution (Outbreak R2) were compared. On 27th December 2021, an index case stayed in restaurant R2 for 98 min. Except for 1 sitting in the same table, six other secondary cases sat in 3 corners at 3 different zones, which were served by different staff. The median exposure time was 34 min (range: 19-98 min). All 7 secondary cases were phylogenetically related to the index. Smoke test demonstrated that the airflow direction may explain the distribution of secondary cases. Compared with an earlier COVID-19 outbreak in another restaurant R1 (19th February 2021), which occurred prior to the mandatory enhancement of indoor air dilution, the secondary attack rate among customers in R2 was significantly lower than that in R1 (3.4%, 7/207 vs 28.9%, 22/76, p<0.001). Enhancement of indoor air dilution through ventilation and installation of air purifier could minimize the risk of SARS-CoV-2 transmission in the restaurants.
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Affiliation(s)
- Vincent Chi-Chung Cheng
- Infection Control Team, Queen Mary Hospital, Hong Kong West Cluster, Hong Kong Special Administrative Region, China; Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
| | - David Christopher Lung
- Department of Pathology, Queen Elizabeth Hospital, Hong Kong Special Administrative Region, China
| | - Shuk-Ching Wong
- Infection Control Team, Queen Mary Hospital, Hong Kong West Cluster, Hong Kong Special Administrative Region, China
| | - Albert Ka-Wing Au
- Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region, China
| | - Qun Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Hong Chen
- Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region, China
| | - Li Xin
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Allen Wing-Ho Chu
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Jonathan Daniel Ip
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Wan-Mui Chan
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Hoi-Wah Tsoi
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Herman Tse
- Department of Pathology, Hong Kong Children's Hospital, Hong Kong Special Administrative Region, China
| | - Ken Ho-Leung Ng
- Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region, China
| | - Mike Yat-Wah Kwan
- Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital, Hong Kong Special Administrative Region, China
| | - Shuk-Kwan Chuang
- Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region, China
| | - Kelvin Kai-Wang To
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Kwok-Yung Yuen
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
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Guo Y, Zhang N, Hu T, Wang Z, Zhang Y. Optimization of energy efficiency and COVID-19 pandemic control in different indoor environments. Energy Build 2022; 261:111954. [PMID: 35185270 PMCID: PMC8848536 DOI: 10.1016/j.enbuild.2022.111954] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 01/23/2022] [Accepted: 02/12/2022] [Indexed: 05/11/2023]
Abstract
The COVID-19 pandemic has led to considerable morbidity and mortality, and consumed enormous resources (e.g. energy) to control and prevent the disease. It is crucial to balance infection risk and energy consumption when reducing the spread of infection. In this study, a quantitative human, behavior-based, infection risk-energy consumption model for different indoor environments was developed. An optimal balance point for each indoor environment can be obtained using the anti-problem method. For this study we selected Wangjing Block, one of the most densely populated places in Beijing, as an example. Under the current ventilation standard (30 m3/h/person), prevention and control of the COVID-19 pandemic would be insufficient because the basic reproduction number (R0 ) for students, workers and elders are greater than 1. The optimal required fresh air ventilation rates in most indoor environments are near or below 60 m3/h/person, after considering the combined effects of multiple mitigation measures. In residences, sports buildings and restaurants, the demand for fresh air ventilation rate is relatively high. After our global optimization of infection risk control (R0 ≤ 1), energy consumption can be reduced by 13.7% and 45.1% on weekdays and weekends, respectively, in contrast to a strategy of strict control (R0 = 1 for each indoor environment).
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Affiliation(s)
- Yong Guo
- Department of Building Science, Tsinghua University, Beijing, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Tingrui Hu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Zhenyu Wang
- College of Economics and Management, Beijing University of Technology, Beijing, China
| | - Yinping Zhang
- Department of Building Science, Tsinghua University, Beijing, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing, China
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Abstract
The COVID-19 pandemic is the most severe pandemic caused by a respiratory virus since the 1918 influenza pandemic. As is the case with other respiratory viruses, three modes of transmission have been invoked: contact (direct and through fomites), large droplets and aerosols. This narrative review makes the case that aerosol transmission is an important mode for COVID-19, through reviewing studies about bioaerosol physiology, detection of infectious SARS-CoV-2 in exhaled bioaerosols, prolonged SARS-CoV-2 infectivity persistence in aerosols created in the laboratory, detection of SARS-CoV-2 in air samples, investigation of outbreaks with manifest involvement of aerosols, and animal model experiments. SARS-CoV-2 joins influenza A virus as a virus with proven pandemic capacity that can be spread by the aerosol route. This has profound implications for the control of the current pandemic and for future pandemic preparedness.
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Affiliation(s)
- Raymond Tellier
- Department of Medicine, McGill University, Montreal, Quebec, Canada
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35
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Schilling-Loeffler K, Falkenhagen A, Johne R. Coronaviruses are stable on glass, but are eliminated by manual dishwashing procedures. Food Microbiol 2022; 106:104036. [PMID: 35690440 PMCID: PMC8986060 DOI: 10.1016/j.fm.2022.104036] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/01/2022] [Accepted: 04/01/2022] [Indexed: 11/29/2022]
Abstract
Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is primarily transmitted from human to human via droplets and aerosols. While transmission via contaminated surfaces is also considered possible, the overall risk of this transmission route is assumed to be low. Nevertheless, transmission through contaminated drinking glasses may pose an increased risk as the glass is in direct contact with the mouth and oral cavity. Using human coronavirus 229E (HCoV-229E) as surrogate for SARS-CoV-2, this study examined coronavirus stability on glass, inactivation by dishwashing detergents, and virus elimination by a manual glass scrubbing device. Infectious HCoV-229E was recovered from glass for 7 and 21 days of storage under daylight and dark conditions, respectively. Near complete inactivation of HCoV-229E (>4 log10 reduction) was observed after incubation with two common dishwashing detergents at room temperature for 15 s, whereas incubation at 43 °C for 60 s was necessary for a third detergent to achieve a similar titer reduction. The virus was efficiently removed from contaminated drinking glasses using a manual glass scrubbing device in accordance with German standard DIN 6653-3. The results confirm that coronaviruses are relatively stable on glass, but indicate that common manual dishwashing procedures can efficiently eliminate coronaviruses from drinking glasses.
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Abstract
COVID-19 has threatened human lives. Countries have implemented various interventions such as vaccination, mask-wearing, body temperature screening, and isolation. However, the effectiveness of single and combined interventions has not yet been accurately analyzed. In this study, an improved SEIR model considering both real human indoor close contact behaviors and susceptibility to COVID-19 was established. Taking Hong Kong as an example, a quantitative assessment of the relationship between the efficiency of single and combined interventions and implementation time and intensity was carried out. The results showed that the infection risk (one-hour close contact with an infected person) of COVID-19 of students, workers, and non-workers/non-students was 3.1%, 8.7%, and 13.6%, respectively. Workplace closures were more effective among built environment interventions. If mask-wearing was mandatorily required in schools, workplaces, supermarkets, shopping centers, and public transport, COVID-19 could not be totally restricted. Workers should be prioritized for vaccination, followed by non-workers/non-students and students. Among all interventions, reducing close contact rate and increasing vaccination rate were better interventions. There was no COVID-19 outbreak (basic reproduction number R0 = 1) if the close contact reduction rate was 59.9% or the vaccination rate reached 89.5%. The results may provide scientific support for COVID-19 prevention and control.
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37
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Cheng P, Luo K, Xiao S, Yang H, Hang J, Ou C, Cowling BJ, Yen HL, Hui DS, Hu S, Li Y. Predominant airborne transmission and insignificant fomite transmission of SARS-CoV-2 in a two-bus COVID-19 outbreak originating from the same pre-symptomatic index case. J Hazard Mater 2022; 425:128051. [PMID: 34910996 PMCID: PMC8656245 DOI: 10.1016/j.jhazmat.2021.128051] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/06/2021] [Accepted: 12/07/2021] [Indexed: 05/22/2023]
Abstract
The number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to increase worldwide, but despite extensive research, there remains significant uncertainty about the predominant routes of SARS-CoV-2 transmission. We conducted a mechanistic modeling and calculated the exposure dose and infection risk of each passenger in a two-bus COVID-19 outbreak in Hunan province, China. This outbreak originated from a single pre-symptomatic index case. Some human behavioral data related to exposure including boarding and alighting time of some passengers and seating position and mask wearing of all passengers were obtained from the available closed-circuit television images/clips and/or questionnaire survey. Least-squares fitting was performed to explore the effect of effective viral load on transmission risk, and the most likely quanta generation rate was also estimated. This study reveals the leading role of airborne SARS-CoV-2 transmission and negligible role of fomite transmission in a poorly ventilated indoor environment, highlighting the need for more targeted interventions in such environments. The quanta generation rate of the index case differed by a factor of 1.8 on the two buses and transmission occurred in the afternoon of the same day, indicating a time-varying effective viral load within a short period of five hours.
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Affiliation(s)
- Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Kaiwei Luo
- Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Shenglan Xiao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China; School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Hongyu Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | | | - Hui-Ling Yen
- School of Public Health, The University of Hong Kong, Hong Kong, China
| | - David Sc Hui
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China
| | - Shixiong Hu
- Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China; School of Public Health, The University of Hong Kong, Hong Kong, China.
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38
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Chen W, Qian H, Zhang N, Liu F, Liu L, Li Y. Extended short-range airborne transmission of respiratory infections. J Hazard Mater 2022; 422:126837. [PMID: 34399209 PMCID: PMC8342890 DOI: 10.1016/j.jhazmat.2021.126837] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 05/09/2023]
Abstract
Debate and scientific inquiries regarding airborne transmission of respiratory infections such as COVID-19 and influenza continue. Health authorities including the WHO and the US CDC have recognized the airborne transmission of COVID-19 in specific settings, although the ventilation requirements remain to be determined. In this work we consider the long-range airborne transmission as an extended short-range airborne route, which reconciles the link between short- and long-range airborne routes. The effective short-range distance is defined as the distance in short range at which long-range route has the same volumetric exposure value as that due to short-range route. Our data show that a decrease in ventilation rate or room volume per person, or an increase in the ratio of the number of infected to susceptible people reduces the effective short-range distance. In a normal breathing scenario with one out of five people infected and a room volume of 12 m3 per person to ensure an effective short-range distance of 1.5 m, a ventilation rate of 10 L/s per person is needed for a duration of 2 h. Our results suggest that effective environmental prevention strategies for respiratory infections require appropriate increases in the ventilation rate while maintaining a sufficiently low occupancy. PRACTICAL IMPLICATIONS: Demonstration of the long-range airborne route as an extended short-range airborne route suggests the significant role played by building ventilation in respiratory infection exposure. The reconciliation of short- and long-range airborne transmission suggests that the commonly observed dominance of close-contact transmission is a probable evidence of short-range airborne transmission, following a separate earlier study that revealed the relative insignificance of large droplet transmission in comparison with the short-range airborne-route. Existing ventilation standards do not account for respiratory infection control, and this study presents a possible approach to account for infection under new ventilation standards.
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Affiliation(s)
- Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Fan Liu
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
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Zhang N, Lei H, Li L, Jin T, Liu X, Miao D, Su B, Bu Z, Fan L, Xue P, Xie J, Li Y. COVID-19 Vaccination Did Not Change the Personal Protective Behaviors of Healthcare Workers in China. Front Public Health 2022; 9:777426. [PMID: 34993170 PMCID: PMC8724136 DOI: 10.3389/fpubh.2021.777426] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 11/30/2021] [Indexed: 01/01/2023] Open
Abstract
Personal protective behaviors of healthcare workers (HCWs) and dynamic changes in them are known to play a major role in the hospital transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, 1,499 HCWs in Chinese hospitals completed an online survey about their knowledge on SARS-CoV-2 transmission and their personal protective behaviors before and after coronavirus disease 2019 (COVID-19) vaccination. Of all the respondents, 89% were vaccinated at the time of the survey and 96% believed that the vaccine was effective or highly effective. Further, 88% of the vaccinated HCWs expressed that they would get revaccinated if the vaccination failed. Compared with HCWs with a lower education level, those with a higher education level had less fear of being infected with SARS-CoV-2 and reported a lower negative impact of the pandemic on how they treated patients. Physicians and nurses were willing to believe that short-range airborne and long-range fomite are possible transmission routes. HCWs with a higher education level had a better knowledge of COVID-19 but worse personal protective behaviors. The fact that HCWs with a longer work experience had worse personal protective behaviors showed that HCWs gradually relax their personal protective behaviors over time. Moreover, vaccination reduced the negative effects of the COVID-19 pandemic on how the HCWs treated patients. Importantly, the survey revealed that after vaccination, HCWs in China did not relax their personal protective behaviors, and it may bring a low potential risk for following waves of variant virus (e.g., delta).
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Hao Lei
- School of Public Health, Zhejiang University, Hangzhou, China
| | - Li Li
- China CDC Key Laboratory of Environment and Population Health, National Institute of Environmental Health, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Doudou Miao
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Boni Su
- Department of Clean Energy Research, China Electric Power Planning and Engineering Institute, Beijing, China
| | - Zhongming Bu
- Department of Energy and Environmental System Engineering, Zhejiang University of Science and Technology, Hangzhou, China
| | - Lin Fan
- China CDC Key Laboratory of Environment and Population Health, National Institute of Environmental Health, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Peng Xue
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Jingchao Xie
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Takahashi S, Kitazawa M, Yoshikawa A. School Virus Infection Simulator for customizing school schedules during COVID-19. Inform Med Unlocked 2022; 33:101084. [PMID: 36120392 DOI: 10.1016/j.imu.2022.101084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 11/22/2022] Open
Abstract
Even as the COVID-19 pandemic raged worldwide, schools strived to provide consistent education to their students. In such situations, schools require customized schedules that can address the health concerns and safety of the students to safely reopen and remain open. School schedules can be customized in many ways, and different approaches' impact on education and effectiveness in reducing infectious risks are different. To address this issue, we developed the School Virus Infection Simulation-Model (SVISM) for teachers and education policymakers. By taking into account the students' lesson schedules, classroom volume, air circulation rates in the classrooms, and infectability of the students, SVISM simulates the spread of infection at a school. We demonstrate the impact of several school schedules in self-contained and departmentalized classrooms and evaluate them in terms of the maximum number of students infected simultaneously, and the percentage of face-to-face lessons. The results show that the impact of increasing the classroom ventilation rate is not as stable as that of customizing school schedules. In addition, school schedules can differently impact the maximum number of students infected simultaneously, depending on whether classrooms are self-contained or departmentalized. We found that the maximum number of students infected simultaneously under a certain schedule with 50 percentage of face-to-face lessons in self-contained classrooms is higher than the maximum number of students infected simultaneously having schedules with a higher percentage of face-to-face lessons; this phenomenon was not found in departmentalized classrooms. These results show that the SVISM can help teachers and education policymakers plan school schedules appropriately to reduce the maximum number of students infected simultaneously, while also maintaining a certain rate of face-to-face lessons.
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Zhang N, Liu X, Jin T, Zhao P, Miao D, Lei H, Su B, Xue P, Xie J, Li Y. Weakening personal protective behavior by Chinese university students after COVID-19 vaccination. Build Environ 2021; 206:108367. [PMID: 34566244 PMCID: PMC8450227 DOI: 10.1016/j.buildenv.2021.108367] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 05/14/2023]
Abstract
Personal protective behaviors and their dynamic change are known to play a major role in the community spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal pathogen of the coronavirus disease 2019 (COVID-19) pandemic. In this study, a total of 3229 students in Chinese universities completed an online survey about their knowledge on transmission and personal protective behavior before and after COVID-19 vaccination. Of the respondents, 87.6% had been vaccinated. Most students believed that the large droplet (97.0%) and short-range airborne (89.3%) routes were the two most likely SARS-CoV-2 transmission routes, whereas only 24.1% considered long-range airborne transmission to be possible. Students who would be expected to possess better knowledge about virus transmission (e.g., students of medicine) reported better personal protective behaviors. Female students reported relatively better personal hygiene practices than male students, so did the confident students than their diffident peers. Students washed their hands on average of 5.76 times per day during the pandemic. Students at universities in southern regions washed their hands more frequently but paid less attention to indoor ventilation than did their northern counterparts. Interestingly, students who are fear of being infected had the bad personal hygiene. University students wore 22% less masks in public indoor environments after vaccination. Chinese university students weakened their personal protective behavior after vaccination and it may increase the potential risk of infection in the new waves of variant virus (e.g. delta).
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Pengcheng Zhao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, SAR, China
| | - Doudou Miao
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Hao Lei
- School of Public Health, Zhejiang University, Hangzhou, Zhejiang, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Peng Xue
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Jingchao Xie
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, SAR, China
- School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, SAR, China
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42
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Coleman KK, Tay DJW, Sen Tan K, Ong SWX, Son TT, Koh MH, Chin YQ, Nasir H, Mak TM, Chu JJH, Milton DK, Chow VTK, Tambyah PA, Chen M, Wai TK. Viral Load of SARS-CoV-2 in Respiratory Aerosols Emitted by COVID-19 Patients while Breathing, Talking, and Singing. Clin Infect Dis 2021; 74:1722-1728. [PMID: 34358292 PMCID: PMC8436389 DOI: 10.1093/cid/ciab691] [Citation(s) in RCA: 98] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Indexed: 11/14/2022] Open
Abstract
Background Multiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing. Methods Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. Results Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of the total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. Conclusions Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging, and whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.
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Affiliation(s)
- Kristen K Coleman
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore
| | - Douglas Jie Wen Tay
- Department of the Built Environment, National University of Singapore, Singapore
| | - Kai Sen Tan
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Sean Wei Xiang Ong
- National Centre for Infectious Diseases, Singapore.,Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - Than The Son
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore.,Department of the Built Environment, National University of Singapore, Singapore
| | - Ming Hui Koh
- Department of the Built Environment, National University of Singapore, Singapore
| | - Yi Qing Chin
- National Centre for Infectious Diseases, Singapore
| | - Haziq Nasir
- Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Tze Minn Mak
- National Centre for Infectious Diseases, Singapore
| | - Justin Jang Hann Chu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Donald K Milton
- Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, USA
| | - Vincent T K Chow
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Paul Anantharajah Tambyah
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Mark Chen
- National Centre for Infectious Diseases, Singapore.,Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - Tham Kwok Wai
- Department of the Built Environment, National University of Singapore, Singapore
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