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Strydom D, le Roux JD, Craig IK. State estimation for nonlinear state-space transmission models of tuberculosis. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2023; 43:339-357. [PMID: 35165919 DOI: 10.1111/risa.13901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Given the high prevalence of tuberculosis (TB) and the mortality rate associated with the disease, numerous models, such as the Gammaitoni and Nucci (GN) model, were developed to model the risk of transmission. These models typically rely on a quanta generation rate as a measurement of infectivity. Since the quanta generation rate cannot be measured directly, the unique contribution of this work is to develop state estimators to estimate the quanta generation rate from available measurements. To estimate the quanta generation rate, the GN model is adapted into an augmented single-room GN model and a simplified two-room GN model. Both models are shown to be observable, i.e., it is theoretically possible to estimate the quanta generation rate given available measurements. Kalman filters are used to estimate the quanta generation rate. First, a continuous-time extended Kalman filter is used for both adapted models using a simulation and measurement sampling rate of 60 s. Accurate quanta generate rate estimates are achieved in both cases. A more realistic scenario is also considered with a measurement sampling rate of one day. For these estimates, a hybrid extended Kalman filter (HEKF) is used. Accurate quanta generation rate estimates are achieved for the more realistic scenario. Future work could potentially use the HEKFs, the adapted models, and real-time measurements in a control system feedback loop to reduce the transmission of TB in confined spaces such as hospitals.
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Affiliation(s)
- Duayne Strydom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
| | - Johan Derik le Roux
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
| | - Ian Keith Craig
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
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Bang JI, Kim JH, Choi A, Sung M. The Wavelength-Based Inactivation Effects of a Light-Emitting Diode Module on Indoor Microorganisms. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:9659. [PMID: 35955018 PMCID: PMC9368635 DOI: 10.3390/ijerph19159659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/03/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
With the increased incidence of infectious disease outbreaks in recent years such as the COVID-19 pandemic, related research is being conducted on the need to prevent their spread; it is also necessary to develop more general physical-chemical control methods to manage them. Consequently, research has been carried out on light-emitting diodes (LEDs) as an effective means of light sterilization. In this study, the sterilization effects on four types of representative bacteria and mold that occur indoors, Bacillus subtilis, Escherichia coli, Penicillium chrysogenum, and Cladosporium cladosporidides, were confirmed using LED modules (with wavelengths of 275, 370, 385, and 405 nm). Additionally, power consumption was compared by calculating the time required for 99.9% sterilization of each microorganism. The results showed that the sterilization effect was high, in the order 275, 370, 385, and 405 nm. The sterilization effects at 385 and 405 nm were observed to be similar. Furthermore, when comparing the power consumption required for 99.9% sterilization of each microorganism, the 275 nm LED module required significantly less power than those of other wavelengths. However, at 405 nm, the power consumption required for 99.9% sterilization was less than that at 370 nm; that is, it was more efficient and similar to or less than that at 385 nm. Additionally, because 405 nm can be applied as general lighting, it was considered to have wider applicability and utility compared with UV wavelengths. Consequently, it should be possible to respond to infectious diseases in the environment using LEDs with visible light wavelengths.
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Affiliation(s)
- Jong-Il Bang
- Department of Architectural Engineering, Sejong University, 209 Neungdong-Ro, Gwangjin-Gu, Seoul 05006, Korea
| | - Ji-Hi Kim
- Specialization Strategy Technology Department, EAN Technology Co., Ltd., EAN Institute of Sustainable Technology, 77-gil Teheran-Ro, Gangnam-Gu, Seoul 06159, Korea
| | - Anseop Choi
- Department of Architectural Engineering, Sejong University, 209 Neungdong-Ro, Gwangjin-Gu, Seoul 05006, Korea
| | - Minki Sung
- Department of Architectural Engineering, Sejong University, 209 Neungdong-Ro, Gwangjin-Gu, Seoul 05006, Korea
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Thornton GM, Fleck BA, Fleck N, Kroeker E, Dandnayak D, Zhong L, Hartling L. The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: A systematic review of ultraviolet radiation. PLoS One 2022; 17:e0266487. [PMID: 35395010 PMCID: PMC8992995 DOI: 10.1371/journal.pone.0266487] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 03/22/2022] [Indexed: 01/14/2023] Open
Abstract
Respiratory viruses are capable of transmitting via an aerosol route. Emerging evidence suggests that SARS-CoV-2 which causes COVID-19 can be spread through airborne transmission, particularly in indoor environments with poor ventilation. Heating, ventilation, and air conditioning (HVAC) systems can play a role in mitigating airborne virus transmission. Ultraviolet germicidal irradiation (UVGI), a feature that can be incorporated into HVAC systems, can be used to impede the ability of viruses to replicate and infect a host. We conducted a systematic review of the scientific literature examining the effectiveness of HVAC design features in reducing virus transmission—here we report results for ultraviolet (UV) radiation. We followed international standards for conducting systematic reviews and developed an a priori protocol. We conducted a comprehensive search to January 2021 of published and grey literature using Ovid MEDLINE, Compendex, and Web of Science Core. Two reviewers were involved in study selection, data extraction, and risk of bias assessments. We presented study characteristics and results in evidence tables, and synthesized results across studies narratively. We identified 32 relevant studies published between 1936 and 2020. Research demonstrates that: viruses and bacteriophages are inactivated by UV radiation; increasing UV dose is associated with decreasing survival fraction of viruses and bacteriophages; increasing relative humidity is associated with decreasing susceptibility to UV radiation; UV dose and corresponding survival fraction are affected by airflow pattern, air changes per hour, and UV device location; and UV radiation is associated with decreased transmission in both animal and human studies. While UV radiation has been shown to be effective in inactivating viruses and reducing disease transmission, practical implementation of UVGI in HVAC systems needs to consider airflow patterns, air changes per hour, and UV device location. The majority of the scientific literature is comprised of experimental, laboratory-based studies. Further, a variety of viruses have been examined; however, there are few studies of coronaviruses and none to date of SARS-CoV-2. Future field studies of UVGI systems could address an existing research gap and provide important information on system performance in real-world situations, particularly in the context of the current COVID-19 pandemic. This comprehensive synthesis of the scientific evidence examining the impact of UV radiation on virus transmission can be used to guide implementation of systems to mitigate airborne spread and identify priorities for future research. Trial registration PROSPERO 2020 CRD42020193968.
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Affiliation(s)
- Gail M. Thornton
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
| | - Brian A. Fleck
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
- * E-mail:
| | - Natalie Fleck
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
| | - Emily Kroeker
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
| | - Dhyey Dandnayak
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
| | - Lexuan Zhong
- Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
| | - Lisa Hartling
- Department of Pediatrics, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Canada
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Trmčić A, Demmings E, Kniel K, Wiedmann M, Alcaine S. Food Safety and Employee Health Implications of COVID-19: A Review. J Food Prot 2021; 84:1973-1989. [PMID: 34265068 PMCID: PMC9906301 DOI: 10.4315/jfp-21-201] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 07/14/2021] [Indexed: 11/11/2022]
Abstract
The COVID-19 pandemic has greatly impacted the U.S. food supply and consumer behavior. Food production and processing are being disrupted as illnesses, proactive quarantines, and government-mandated movement restrictions cause labor shortages. In this environment, the food industry has been required to adopt new, additional practices to minimize the risk of COVID-19 cases and outbreaks among its workforce. Successfully overcoming these challenges requires a comprehensive approach that addresses COVID-19 transmission both within and outside the facility. Possible interventions include strategies (i) to vaccinate employees, (ii) to assure that employees practice social distancing, (iii) to assure that employees wear face coverings, (iv) to screen employees for COVID-19, (v) to assure that employees practice frequent hand washing and avoid touching their faces, (vi) to clean frequently touched surfaces, and (vii) to assure proper ventilation. Compliance with these control strategies must be verified, and an overall COVID-19 control culture must be established to implement an effective program. Despite some public misperceptions about the health risk of severe acute respiratory syndrome coronavirus 2 on foods or food packaging, both the virus biology and epidemiological data clearly support a negligible risk of COVID-19 transmission through food and food packing. However, COVID-19 pandemic-related supply chain and workforce disruptions and the shift in resources to protect food industry employees from COVID-19 may increase the actual food safety risks. The goal of this review was to describe the COVID-19 mitigation practices adopted by the food industry and the potential impact of these practices and COVID-19-related disruptions on the industry's food safety mission. A review of these impacts is necessary to ensure that the food industry is prepared to maintain a safe and nutritious food supply in the face of future global disruptions.
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Affiliation(s)
- Aljoša Trmčić
- Department of Food Science, Cornell University, Ithaca, New York 14850
| | | | - Kalmia Kniel
- Department of Animal and Food Sciences, University of Delaware, Newark, Delaware 19716, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, New York 14850
| | - Sam Alcaine
- Department of Food Science, Cornell University, Ithaca, New York 14850,Author for correspondence. Tel: 607-255-9183; Fax: 607-254-4868
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Elsaid AM, Ahmed MS. Indoor Air Quality Strategies for Air-Conditioning and Ventilation Systems with the Spread of the Global Coronavirus (COVID-19) Epidemic: Improvements and Recommendations. ENVIRONMENTAL RESEARCH 2021; 199:111314. [PMID: 34048748 PMCID: PMC8146370 DOI: 10.1016/j.envres.2021.111314] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 05/06/2021] [Indexed: 05/08/2023]
Abstract
The coronavirus has come to the world and spread with great wide among the countries of the world and has resulted in numerous infections that exceeded 167,181,023 million patients and are close to 3.5 deaths by September 2021. It also brought with it panic and fear, halted many activities, and led to the decline of the global economy. It changed human behavior and forced people to change their lifestyles to avoid infection. One of the most sectors that must be taken into consideration through pandemic coronavirus (COVID-19) around the globe is the air conditioning systems. The HVAC systems depend on the air as a heat transfer medium. The air contains a group of pollutants, viruses, and bacteria, and it affects and destroys human life. The air filter plays a major role as an important component in the air conditioning systems. Thus, it requires more effort by researchers to improve its design to prevent the ultra-size of particles loaded with coronavirus (COVID-19). This paper provides insight into the design of existing combined air-conditioners on their suitability and their impact on the spread of the hybrid coronavirus epidemic and review efforts to obtain a highly efficient air filter to get rid of super-sized particles for protection against epidemic infection. In addition, important guideline recommendations have been made to limit the spread of the COVID-19 virus and to obtain indoor air quality in air-conditioned places.
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Affiliation(s)
- Ashraf Mimi Elsaid
- RHVAC Department of Technology, Faculty of Technology and Education, Helwan University, Cairo, 11282, Egypt.
| | - M Salem Ahmed
- Mechanical Power Engineering Department, Faculty of Technology and Education, Sohag University, Egypt
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Effect of a shielded continuous ultraviolet-C air disinfection device on reduction of air and surface microbial contamination in a pediatric oncology outpatient care unit. Am J Infect Control 2019; 47:1248-1254. [PMID: 31053372 DOI: 10.1016/j.ajic.2019.03.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 03/22/2019] [Accepted: 03/23/2019] [Indexed: 12/17/2022]
Abstract
BACKGROUND For a clean hospital environment, we evaluated whether ultraviolet-C (UV-C) air disinfection reduces airborne and surface microbial contamination in an outpatient pediatric oncology center. METHODS A pre- and post-intervention study compared 6 test locations, where continuous shielded UV-C air disinfection devices were installed, with 10 control locations without UV-C. Pre- and post-intervention air and surface samples were collected for bacterial and fungal cultures. Percent changes in colony forming unit (CFU) counts in the test and control locations were compared. RESULTS Mean bacterial CFU count per cubic meter air and per surface contact plates decreased by 27% (P = .219) and 37% (P = .01), respectively, in test locations compared to 40% (P = .054) and 30% (P = .006) reductions in control locations. Mean fungal CFU count per cubic meter air and per surface contact plates increased by 14% (P = .156) and 19% (P = .048), respectively, in test locations compared to 24% (P = .409) and 2% (P = .34) increases in control locations. CONCLUSIONS There were no consistent statistically significant differences in the air and surface culture results between test locations where UV-C devices were installed and control locations. The effectiveness of UV-C air disinfection in reducing air and surface microbial contamination in outpatient clinical areas where immunocompromised children are encountered was not proven.
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Evaluation of UR-UVGI System for Sterilization Effect on Microorganism Contamination in Negative Pressure Isolation Ward. SUSTAINABILITY 2018. [DOI: 10.3390/su10093192] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A negative pressure isolation ward prevents the outflow of airborne microorganisms from inside the ward, minimizing the spread of airborne contamination causing respiratory infection. In response to recent outbreaks of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), Korea has increased the number of these facilities. However, airborne contaminants that flow into the ward from adjacent areas may cause secondary harm to patients. In this study, the sterilization effect of upper-room ultraviolet germicidal irradiation (UR-UVGI) on microorganisms generated within the negative pressure isolation ward and those flowing inward from adjacent areas was evaluated through field experiments and computational fluid dynamics (CFD) analysis, to assess the potential of this approach as a supplementary measure to control such microorganisms. The sterilization effect was found to be not high because of high-level ventilation. CFD analysis under various conditions shows that the sterilization effect for indoor-generated microorganisms varies with the level of UV radiation, the source locations of the indoor-generated microorganisms, air supplies and exhausts, the UVGI system, and the airflow formed under the specified conditions. Our results show that when the UVGI system is installed in the upper part of the ward entrance, contaminated air from adjacent area is strongly sterilized.
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Li Y, Wang M, Guan D, Lv H, Zhao J, Yu X, Yang X, Wu C. A Study on the Decontaminated Efficiency of Ultraviolet Device on the Indoor Airborne Bacteria. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.proeng.2017.10.281] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Rudnick S, McDevitt J, Hunt G, Stawnychy M, Vincent R, Brickner P. Influence of ceiling fan's speed and direction on efficacy of upperroom, ultraviolet germicidal irradiation: Experimental. BUILDING AND ENVIRONMENT 2015; 92:756-763. [PMID: 32288032 PMCID: PMC7127731 DOI: 10.1016/j.buildenv.2014.03.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 03/22/2014] [Accepted: 03/24/2014] [Indexed: 05/22/2023]
Abstract
Increasing a ceiling fan's speed from its lowest setting of 61 rpm, which resulted in 0.77 m3/s of airflow, to its highest setting of 176 rpm, which resulted in 2.5 m3/s of airflow, or having the fan blow either upward or downward had no statistically significant effect on the efficacy of upper-room ultraviolet germicidal irradiation (UVGI). This outcome suggests that air circulation due to the ceiling fan was sufficient and that any additional increase would not improve efficacy. Numerous experimental studies on upper-room UVGI in which fans were used to provide air mixing have been published. However, none have quantified the air movement produced by these fans or described their tests in sufficient detail to allow results to be compared to predictions using computational fluid dynamics (CFD). The present work provides the required information. In addition to the usual boundary conditions needed for CFD, we made experimental measurements of UV susceptibility of the microorganisms used in the upper-room UVGI tests. We measured UV susceptibilities for Mycobacterium parafortuitum and Bacillus atrophaeus spores to be 0.074 and 0.018 m2/J, respectively. In a previous publication, we reported the spatial distribution of fluence rate, which is also needed for predicting efficacy from CFD. In a companion paper referred to as Part II, upper-room UVGI efficacy was predicted by both Eulerian and Lagrangian CFD and compared to the experimental results from the present study.
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Affiliation(s)
- S.N. Rudnick
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - J.J. McDevitt
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - G.M. Hunt
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - M.T. Stawnychy
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - R.L. Vincent
- Department of Medicine, Section of General Internal Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1087, New York, NY 10029, USA
- Corresponding author.
| | - P.W. Brickner
- Department of Medicine, Section of General Internal Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1087, New York, NY 10029, USA
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Gilkeson CA, Noakes C. Application of CFD simulation to predicting upper-room UVGI effectiveness. Photochem Photobiol 2012; 89:799-810. [PMID: 23106610 DOI: 10.1111/php.12013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 10/16/2012] [Indexed: 11/28/2022]
Abstract
This study outlines the potential for Computational Fluid Dynamics (CFD) simulation to be used to predict upper-room ultraviolet germicidal irradiation (UVGI) effectiveness to aid system design and the development of future guidance. A numerical study of two wall-mounted UVGI lamps in a mechanically ventilated test chamber is used to assess the influence of modeling parameters on prediction of dose distribution and microorganism inactivation. Irradiance fields for both UVGI fixtures are obtained via radiometry and implemented in the model. A series of sensitivity studies consider the importance of UVGI field accuracy and computational grid and turbulence model selection. Results show that 2D irradiance fields are sufficient for calculating dose and in-activation, whereas a 1D field is inadequate for modeling purposes. Further parametric studies consider the effects of ventilation parameters, UVGI lamp configuration and microorganism susceptibility. These demonstrate the feasibility of modeling the interaction of the airflow and UV field in a room to quantify the dose distribution. Microorganism in-activation can also be accomplished by employing passive scalars and species transport models, however, further validation data are necessary before this can be used to make reliable quantitative predictions.
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Affiliation(s)
- Carl A Gilkeson
- Pathogen Control Engineering Institute, School of Civil Engineering, University of Leeds, Leeds, UK
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