Airborne transmission of SARS-CoV-2

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo

We employed carbon dioxide (CO2) concentration monitoring using mobile devices to identify location-specific risks for airborne infection transmission. We lent a newly developed, portable Pocket CO2 Logger to 10 participants, to be carried at all times, for an average of 8 days. The participants recorded their location at any given time as cinema, gym, hall, home, hospital, other indoors, other outgoings, pub, restaurant, university, store, transportation, or workplace. Generalized linear mixed model was used for statistical analysis, with the objective variable set to the logarithm of CO2 concentration. Analysis was performed by assigning participant identification as the random effect and location as the fixed effect. The data were collected per participant (seven males, four females), resulting in a total of 12,253 records. Statistical analysis identified three relatively poorly ventilated locations (median values > 1,000 ppm) that contributed significantly (p < 0.0001) to CO2 concentrations: homes (1,316 ppm), halls (1,173 ppm), and gyms (1005ppm). In contrast, two locations were identified to contribute significantly (p < 0.0001) to CO2 concentrations but had relatively low average values (<1,000 ppm): workplaces (705 ppm) and stores (620 ppm). The Pocket CO2 Logger can be used to visualize airborne infectious transmission risk by location to help guide recommendation regarding infectious disease policies, such as restrictions on human flow and ventilation measures and guidelines. In the future, large-scale surveys are expected to utilize the global positioning system, Wi-Fi, or Bluetooth of an individual's smartphone to improve ease and accuracy.

Reducing Transmission of Airborne Respiratory Pathogens: A New Beginning as the COVID-19 Emergency Ends

BACKGROUND

In response to the COVID-19 pandemic, new evidence-based strategies have emerged for reducing transmission of respiratory infections through management of indoor air.

OBJECTIVES

This paper reviews critical advances that could reduce the burden of disease from inhaled pathogens and describes challenges in their implementation.

DISCUSSION

Proven strategies include assuring sufficient ventilation, air cleaning by filtration, and air disinfection by germicidal ultraviolet (UV) light. Layered intervention strategies are needed to maximize risk reduction. Case studies demonstrate how to implement these tools while also revealing barriers to implementation. Future needs include standards designed with infection resilience and equity in mind, buildings optimized for infection resilience among other drivers, new approaches and technologies to improve ventilation, scientific consensus on the amount of ventilation needed to achieve a desired level of risk, methods for evaluating new air-cleaning technologies, studies of their long-term health effects, workforce training on ventilation systems, easier access to federal funds, demonstration projects in schools, and communication with the public about the importance of indoor air quality and actions people can take to improve it. https://doi.org/10.1289/EHP13878.

Elucidating the behavior of the SARS-CoV-2 virus surface at vapor-liquid interfaces using molecular dynamics simulation

Aerosols play a major role in the transmission of the SARS-CoV-2 virus. The behavior of the virus within aerosols is therefore of fundamental importance. On the surface of a SARS-CoV-2 virus, there are about 40 spike proteins, which each have a length of about 20 nm. They are glycosylated trimers, which are highly flexible, due to their structure. These spike proteins play a central role in the intrusion of the virus into human host cells and are, therefore, a focus of vaccine development. In this work, we have studied the behavior of spike proteins of the SARS-CoV-2 virus in the presence of a vapor-liquid interface by molecular dynamics (MD) simulations. Systematically, the behavior of the spike protein at different distances to a vapor-liquid interface were studied. The results reveal that the spike protein of the SARS-CoV-2 virus is repelled from the vapor-liquid interface and has a strong affinity to stay inside the bulk liquid phase. Therefore, the spike protein bends when a vapor-liquid interface approaches the top of the protein. This has important consequences for understanding the behavior of the virus during the dry-out of aerosol droplets.

Toward Standardized Aerovirology: A Critical Review of Existing Results and Methodologies

Understanding the airborne survival of viruses is important for public health and epidemiological modeling and potentially to develop mitigation strategies to minimize the transmission of airborne pathogens. Laboratory experiments typically involve investigating the effects of environmental parameters on the viability or infectivity of a target airborne virus. However, conflicting results among studies are common. Herein, the results of 34 aerovirology studies were compared to identify links between environmental and compositional effects on the viability of airborne viruses. While the specific experimental apparatus was not a factor in variability between reported results, it was determined that the experimental procedure was a major factor that contributed to discrepancies in results. The most significant contributor to variability between studies was poorly defined initial viable virus concentration in the aerosol phase, causing many studies to not measure the rapid inactivation, which occurs quickly after particle generation, leading to conflicting results. Consistently, studies that measured their reference airborne viability minutes after aerosolization reported higher viability at subsequent times, which indicates that there is an initial loss of viability which is not captured in these studies. The composition of the particles which carry the viruses was also found to be important in the viability of airborne viruses; however, the mechanisms for this effect are unknown. Temperature was found to be important for aerosol-phase viability, but there is a lack of experiments that directly compare the effects of temperature in the aerosol phase and the bulk phase. There is a need for repeated measurements between different research groups under identical conditions both to assess the degree of variability between studies and also to attempt to better understand already published data. Lack of experimental standardization has hindered the ability to quantify the differences between studies, for which we provide recommendations for future studies. These recommendations are as follows: measuring the reference airborne viability using the "direct method"; use equipment which maximizes time resolution; quantify all losses appropriately; perform, at least, a 5- and 10-min sample, if possible; report clearly the composition of the virus suspension; measure the composition of the gas throughout the experiment. Implementing these recommendations will address the most significant oversights in the existing literature and produce data which can more easily be quantitatively compared.

Natural products as a source of Coronavirus entry inhibitors

The COVID-19 pandemic has had a significant and lasting impact on the world. Four years on, despite the existence of effective vaccines, the continuous emergence of new SARS-CoV-2 variants remains a challenge for long-term immunity. Additionally, there remain few purpose-built antivirals to protect individuals at risk of severe disease in the event of future coronavirus outbreaks. A promising mechanism of action for novel coronavirus antivirals is the inhibition of viral entry. To facilitate entry, the coronavirus spike glycoprotein interacts with angiotensin converting enzyme 2 (ACE2) on respiratory epithelial cells. Blocking this interaction and consequently viral replication may be an effective strategy for treating infection, however further research is needed to better characterize candidate molecules with antiviral activity before progressing to animal studies and clinical trials. In general, antiviral drugs are developed from purely synthetic compounds or synthetic derivatives of natural products such as plant secondary metabolites. While the former is often favored due to the higher specificity afforded by rational drug design, natural products offer several unique advantages that make them worthy of further study including diverse bioactivity and the ability to work synergistically with other drugs. Accordingly, there has recently been a renewed interest in natural product-derived antivirals in the wake of the COVID-19 pandemic. This review provides a summary of recent research into coronavirus entry inhibitors, with a focus on natural compounds derived from plants, honey, and marine sponges.

Reduction of acute respiratory infections in day-care by non-pharmaceutical interventions: a narrative review

Objective

Children who start in day-care have 2-4 times as many respiratory infections compared to children who are cared for at home, and day-care staff are among the employees with the highest absenteeism. The extensive new knowledge that has been generated in the COVID-19 era should be used in the prevention measures we prioritize. The purpose of this narrative review is to answer the questions: Which respiratory viruses are the most significant in day-care centers and similar indoor environments? What do we know about the transmission route of these viruses? What evidence is there for the effectiveness of different non-pharmaceutical prevention measures?

Design

Literature searches with different terms related to respiratory infections in humans, mitigation strategies, viral transmission mechanisms, and with special focus on day-care, kindergarten or child nurseries, were conducted in PubMed database and Web of Science. Searches with each of the main viruses in combination with transmission, infectivity, and infectious spread were conducted separately supplemented through the references of articles that were retrieved.

Results

Five viruses were found to be responsible for ≈95% of respiratory infections: rhinovirus, (RV), influenza virus (IV), respiratory syncytial virus (RSV), coronavirus (CoV), and adenovirus (AdV). Novel research, emerged during the COVID-19 pandemic, suggests that most respiratory viruses are primarily transmitted in an airborne manner carried by aerosols (microdroplets).

Conclusion

Since airborne transmission is dominant for the most common respiratory viruses, the most important preventive measures consist of better indoor air quality that reduces viral concentrations and viability by appropriate ventilation strategies. Furthermore, control of the relative humidity and temperature, which ensures optimal respiratory functionality and, together with low resident density (or mask use) and increased time outdoors, can reduce the occurrence of respiratory infections.

Risk factors for SARS-CoV-2 transmission during a movie theater outbreak in Incheon in the Republic of Korea, November 2021: a retrospective study

BACKGROUND

We examined factors contributing to the transmission of an acute respiratory virus within multi-use facilities, focusing on an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a movie theater in the Republic of Korea.

METHODS

This retrospective cohort study involved a descriptive analysis of 48 confirmed cases. Logistic regression was applied to a cohort of 80 theater attendees to identify risk factors for infection. The infection source and transmission route were determined through gene sequencing data analysis.

RESULTS

Of the 48 confirmed cases, 35 were theater attendees (72.9%), 10 were family members of attendees (20.8%), 2 were friends (4.2%), and 1 was an employee (2.1%). Among the 80 individuals who attended the 3rd to 5th screenings of the day, 35 became infected, representing a 43.8% attack rate. Specifically, 28 of the 33 third-screening attendees developed confirmed SARSCoV-2, constituting an 84.8% attack rate. Furthermore, 11 of the 12 cases epidemiologically linked to the theater outbreak were clustered monophyletically within the AY.69 lineage. At the time of the screening, 35 individuals (72.9%) had received 2 vaccine doses. However, vaccination status did not significantly influence infection risk. Multivariate analysis revealed that close contacts had a 15.9-fold higher risk of infection (95% confidence interval, 4.37-78.39) than casual contacts.

CONCLUSION

SARS-CoV-2 transmission occurred within the theater, and extended into the community, via a moviegoer who attended the 3rd screening during the viral incubation period after contracting the virus from a family member. This study emphasizes the importance of adequate ventilation in theaters.

Study of aerosol dispersion and control in dental practice

OBJECTIVES

In this study, we investigated the dispersion patterns of aerosols and droplets in dental clinics and developed a suction device to evaluate its effectiveness in reducing aerosols during dental procedures.

MATERIALS AND METHODS

Firstly, the continuous images of oral aerosols and droplets were photographed with a high-speed camera, and the trajectories of these particles were recognized and processed by Image J to determine key parameters affecting particle dispersion: diffusion velocity, distance, and angle. Secondly, based on the parameter data, the flow field of aerosol particles around the oral cavity was simulated using computational fluid dynamics (CFD), and the flow field under adsorption conditions was simulated to demonstrate the aerodynamic characteristics and capture efficiencies of the single-channel and three-channel adsorption ports at different pressures. Finally, according to the simulated data, a three-channel suction device was developed, and the capture efficiency of the device was tested by the fluorescein tracer method.

RESULTS

The dispersion experimental data showed that aerosol particles' maximum diffusion velocity, distance, and angle were 6.2 m/s, 0.55 m, and 130°, respectively. The simulated aerosol flow-field distribution was consistent with the aerosol dispersion patterns. The adsorption simulation results showed that the outlet flow rate of single-channel adsorption was 184.5 L/s at - 350 Pa, and the aerosol capture efficiency could reach 79.4%. At - 350 Pa and - 150 Pa, the outlet flow rate of three-channel adsorption was 228.9 L/s, and the capture efficiency was 99.23%. The adsorption experimental data showed that the capture efficiency of three-channel suction device was 97.71%.

CONCLUSIONS

A three-channel suction device was designed by simulations and experiments, which can capture most aerosols in the dental clinic and prevent them from spreading.

CLINICAL RELEVANCE

Using three-channel suction devices during oral treatment effectively reduces the spread of oral aerosols, which is essential to prevent the spread of epidemics and ensure the health and safety of patients and dental staff.

Respiratory particle emission rates from children during speaking

The number of respiratory particles emitted during different respiratory activities is one of the main parameters affecting the airborne transmission of respiratory pathogens. Information on respiratory particle emission rates is mostly available for adults (few studies have investigated adolescents and children) and generally involves a limited number of subjects. In the present paper we attempted to reduce this knowledge gap by conducting an extensive experimental campaign to measure the emission of respiratory particles of more than 400 children aged 6 to 12 years while they pronounced a phonetically balanced word list at two different voice intensity levels ("speaking" and "loudly speaking"). Respiratory particle concentrations, particle distributions, and exhaled air flow rates were measured to estimate the respiratory particle emission rate. Sound pressure levels were also simultaneously measured. We found out that median respiratory particle emission rates for speaking and loudly speaking were 26 particles s-1 (range 7.1-93 particles s-1) and 41 particles s-1 (range 10-146 particles s-1), respectively. Children sex was significant for emission rates, with higher emission rates for males during both speaking and loudly speaking. No effect of age on the emission rates was identified. Concerning particle size distributions, for both respiratory activities, a main mode at approximately 0.6 µm and a second minor mode at < 2 µm were observed, and no differences were found between males and females. This information provides important input parameters in predictive models adopted to estimate the transmission risk of airborne pathogens in indoor spaces.

Airborne influenza virus shedding by patients in health care units: Removal mechanisms affecting virus transmission

In this study, we characterize the distribution of airborne viruses (influenza A/B) in hospital rooms of patients with confirmed infections. Concurrently, we monitored fine particulate matter (PM2.5 & PM10) and several physical parameters including the room air exchange rate, temperature, and relative humidity to identify corresponding correlations with virus transport and removal determinants. The results continue to raise concerns about indoor air quality (IAQ) in healthcare facilities and the potential exposure of patients, staff and visitors to aerosolized viruses as well as elevated indoor PM levels caused by outdoor sources and/or re-suspension of settled particles by indoor activities. The influenza A virus was detected in 42% of 33 monitored rooms, with viruses detectible up to 1.5 m away from the infected patient. Active coughing was a statistically significant variable that contributed to a higher positive rate of virus detection in the collected air samples. Viral load across patient rooms ranged between 222 and 5,760 copies/m3, with a mean of 820 copies/m3. Measured PM2.5 and PM10 levels exceeded IAQ daily exposure guidelines in most monitored rooms. Statistical and numerical analyses showed that dispersion was the dominant viral removal pathway followed by settling. Changes in the relative humidity and the room's temperature were had a significant impact on the viral load removal. In closure, we highlight the need for an integrated approach to control determinants of IAQ in patients' rooms.

Detection of SARS-CoV-2 in high-efficiency particulate air (HEPA) filters of low-cost air purifiers in community-based organizations

This study aims to investigate the presence of SARS-CoV-2 in public spaces and assess the utility of inexpensive air purifiers equipped with high-efficiency particulate air (HEPA) filters for viral detection. Samples were collected from six community-based organizations in underserved minority neighborhoods in Northwest Miami, Florida, from February to May 2022. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect SARS-CoV-2 in air purifier filters and surface swabs. Among 32 filters tested, three yielded positive results, while no positive surface swabs were found. Notably, positive samples were obtained exclusively from child daycare centers. These findings highlight the potential for airborne transmission of SARS-CoV-2 in indoor air, particularly in child daycare centers. Moreover, the study demonstrates the effectiveness of readily available HEPA filters in detecting the virus. Improving indoor ventilation and implementing air filtration systems are crucial in reducing COVID-19 transmission where people gather. Air filtration systems incorporating HEPA filters offer a valuable approach to virus detection and reducing transmission risks. Future research should explore the applicability of this technology for early identification and mitigation of viral outbreaks.

Diathermy and bone sawing are high aerosol yield procedures

Aims

Orthopaedic surgery uses many varied instruments with high-speed, high-impact, thermal energy and sometimes heavy instruments, all of which potentially result in aerosolization of contaminated blood, tissue, and bone, raising concerns for clinicians' health. This study quantifies the aerosol exposure by measuring the number and size distribution of the particles reaching the lead surgeon during key orthopaedic operations.

Methods

The aerosol yield from 17 orthopaedic open surgeries (on the knee, hip, and shoulder) was recorded at the position of the lead surgeon using an Aerodynamic Particle Sizer (APS; 0.5 to 20 μm diameter particles) sampling at 1 s time resolution. Through timestamping, detected aerosol was attributed to specific procedures.

Results

Diathermy (electrocautery) and oscillating bone saw use had a high aerosol yield (> 100 particles detected per s) consistent with high exposure to aerosol in the respirable range (< 5 µm) for the lead surgeon. Pulsed lavage, reaming, osteotome use, and jig application/removal were medium aerosol yield (10 to 100 particles s-1). However, pulsed lavage aerosol was largely attributed to the saline jet, osteotome use was always brief, and jig application/removal had a large variability in the associated aerosol yield. Suctioning (with/without saline irrigation) had a low aerosol yield (< 10 particles s-1). Most surprisingly, other high-speed procedures, such as drilling and screwing, had low aerosol yields.

Conclusion

This work suggests that additional precautions should be recommended for diathermy and bone sawing, such as enhanced personal protective equipment or the use of suction devices to reduce exposure.

Review of animal transmission experiments of respiratory viruses: Implications for transmission risk of SARS-COV-2 in humans via different routes

Exploring transmission risk of different routes has major implications for epidemic control. However, disciplinary boundaries have impeded the dissemination of epidemic information, have caused public panic about "air transmission," "air-conditioning transmission," and "environment-to-human transmission," and have triggered "hygiene theater." Animal experiments provide experimental evidence for virus transmission, but more attention is paid to whether transmission is driven by droplets or aerosols and using the dichotomy to describe most transmission events. Here, according to characteristics of experiment setups, combined with patterns of human social interactions, we reviewed and grouped animal transmission experiments into four categories-close contact, short-range, fomite, and aerosol exposure experiments-and provided enlightenment, with experimental evidence, on the transmission risk of severe acute respiratory syndrome coronavirus (SARS-COV-2) in humans via different routes. When referring to "air transmission," context should be showed in elaboration results, rather than whether close contact, short or long range is uniformly described as "air transmission." Close contact and short range are the major routes. When face-to-face, unprotected, horizontally directional airflow does promote transmission, due to virus decay and dilution in air, the probability of "air conditioning transmission" is low; the risk of "environment-to-human transmission" highly relies on surface contamination and human behavior based on indirect path of "fomite-hand-mucosa or conjunctiva" and virus decay on surfaces. Thus, when discussing the transmission risk of SARS-CoV-2, we should comprehensively consider the biological basis of virus transmission, environmental conditions, and virus decay. Otherwise, risk of certain transmission routes, such as long-range and fomite transmission, will be overrated, causing public excessive panic, triggering ineffective actions, and wasting epidemic prevention resources.

Evaluation of aerosols in a simulated orthodontic debanding procedure

Dental practitioners may be at risk for exposure to severe acute respiratory syndrome corona virus 2 when performing aerosol generating procedures. Though recent evidence suggests that coronavirus may be transmitted through aerosol generating procedures, it is unknown whether common procedures performed in dental clinics generate aerosol. The aim of this study was to simultaneously quantify airborne concentrations of the bacteriophage MS2 near the oral cavity of a dental mannequin and behind personal protective equipment (i.e., face shield) of the practitioner during a simulated orthodontic debanding procedure. A deband was performed eight times on a dental mannequin. Optical particle counters and SKC Biosamplers were used to measure particle concentration and to collect virus aerosol generated during the procedure, both near the oral cavity and behind the orthodontists face shield. A plaque assay was used to determine the viable virus airborne concentration. When comparing the two measuring locations, near the oral cavity and behind the clinician's face shield, there was no statistically significant difference of virus concentrations or particle size distribution. This study suggests that debanding under these conditions generates live virus aerosol and a face shield does not provide increased protection from virus aerosol, but does provide some protection against splatter during the procedure.

Mechanisms controlling the transport and evaporation of human exhaled respiratory droplets containing the severe acute respiratory syndrome coronavirus: a review

Transmission of the coronavirus disease 2019 is still ongoing despite mass vaccination, lockdowns, and other drastic measures to control the pandemic. This is due partly to our lack of understanding on the multiphase flow mechanics that control droplet transport and viral transmission dynamics. Various models of droplet evaporation have been reported, yet there is still limited knowledge about the influence of physicochemical parameters on the transport of respiratory droplets carrying the severe acute respiratory syndrome coronavirus 2. Here we review the effects of initial droplet size, environmental conditions, virus mutation, and non-volatile components on droplet evaporation and dispersion, and on virus stability. We present experimental and computational methods to analyze droplet transport, and factors controlling transport and evaporation. Methods include thermal manikins, flow techniques, aerosol-generating techniques, nucleic acid-based assays, antibody-based assays, polymerase chain reaction, loop-mediated isothermal amplification, field-effect transistor-based assay, and discrete and gas-phase modeling. Controlling factors include environmental conditions, turbulence, ventilation, ambient temperature, relative humidity, droplet size distribution, non-volatile components, evaporation and mutation. Current results show that medium-sized droplets, e.g., 50 µm, are sensitive to relative humidity. Medium-sized droplets experience delayed evaporation at high relative humidity, and increase airborne lifetime and travel distance. By contrast, at low relative humidity, medium-sized droplets quickly shrink to droplet nuclei and follow the cough jet. Virus inactivation within a few hours generally occurs at temperatures above 40 °C, and the presence of viral particles in aerosols impedes droplet evaporation.

Transmission of SARS-CoV-2 in the workplace: Key findings from a rapid review of the literature

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.

Methine initiated polypropylene-based disposable face masks aging validated by micromechanical properties loss of atomic force microscopy

The contagious coronavirus disease-2019 pandemic has led to an increasing number of disposable face masks (DFMs) abandoned in the environment, when they are exposed to the air condition, the broken of chemical bond induced aging is inevitably occurred which meantime would cause a drastic decrease of the mechanical flexibility. However, the understanding of between chemical bond change related to aging and its micromechanical loss is limited due to the lack of refined techniques. Herein, the atomic force microscopy (AFM) technique was firstly used to observe the aging process induced by methine of the polypropylene-based DFMs. By comparing the micromechanical properties loss, the influences of humidity and light density on the DFM aging were systematically studied in the early 72 h, and it revealed that the increasing scissions number of the easiest attacked methine (C^t-H) can gradually decrease the micromechanical properties of the polypropylene (PP)-based DFM. Furthermore, the results are also validated by the in- situ FTIR and XPS analysis. This work discloses that an aging process can be initially estimated with the micromechanical changes observed by AFM, which offers fundamental data to manage this important emerging plastic pollution during COVID-19 pandemic.

Safe distancing in the time of COVID-19

The spread of viruses such as SARS-CoV-2 brought new challenges to our society, including a stronger focus on safety across all businesses. Many countries have imposed a minimum social distance among people in order to ensure their safety. This brings new challenges to many customer-related businesses, such as restaurants, offices, theaters, etc., on how to locate their facilities (tables, seats etc.) under distancing constraints. We propose a parallel between this problem and that of locating wind turbines in an offshore area. The discovery of this parallel allows us to apply Mathematical Optimization algorithms originally designed for wind farms, to produce optimized facility layouts that minimize the overall risk of infection among customers. In this way we can investigate the structure of the safest layouts, with some surprising outcomes. A lesson learned is that, in the safest layouts, the facilities are not equally distanced (as it is typically believed) but tend to concentrate on the border of the available area-a policy that significantly reduces the overall risk of contagion.

Surveillance of SARS-CoV-2 in nine neighborhood sewersheds in Detroit Tri-County area, United States: Assessing per capita SARS-CoV-2 estimations and COVID-19 incidence

Wastewater-based epidemiology (WBE) has been suggested as a useful tool to predict the emergence and investigate the extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, we screened appropriate population biomarkers for wastewater SARS-CoV-2 normalization and compared the normalized SARS-CoV-2 values across locations with different demographic characteristics in southeastern Michigan. Wastewater samples were collected between December 2020 and October 2021 from nine neighborhood sewersheds in the Detroit Tri-County area. Using reverse transcriptase droplet digital polymerase chain reaction (RT-ddPCR), concentrations of N1 and N2 genes in the studied sites were quantified, with N1 values ranging from 1.92 × 10² genomic copies/L to 6.87 × 10³ gc/L and N2 values ranging from 1.91 × 10² gc/L to 6.45 × 10³ gc/L. The strongest correlations were observed with between cumulative COVID-19 cases per capita (referred as COVID-19 incidences thereafter), and SARS-CoV-2 concentrations normalized by total Kjeldahl nitrogen (TKN), creatinine, 5-hydroxyindoleacetic acid (5-HIAA) and xanthine when correlating the per capita SARS-CoV-2 and COVID-19 incidences. When SARS-CoV-2 concentrations in wastewater were normalized and compared with COVID-19 incidences, the differences between neighborhoods of varying demographics were reduced as compared to differences observed when comparing non-normalized SARS-CoV-2 with COVID-19 cases. This indicates when studying the disease burden in communities of different demographics, accurate per capita estimation is of great importance. The study suggests that monitoring selected water quality parameters or biomarkers, along with RNA concentrations in wastewater, will allow adequate data normalization for spatial comparisons, especially in areas where detailed sanitary sewage flows and contributing populations in the catchment areas are not available. This opens the possibility of using WBE to assess community infections in rural areas or the developing world where the contributing population of a sample could be unknown.

A single intranasal administration of AdCOVID protects against SARS-CoV-2 infection in the upper and lower respiratory tracts

The coronavirus disease 2019 (COVID-19) pandemic has illustrated the critical need for effective prophylactic vaccination to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Intranasal vaccination is an attractive approach for preventing COVID-19 as the nasal mucosa is the site of initial SARS-CoV-2 entry and viral replication prior to aspiration into the lungs. We previously demonstrated that a single intranasal administration of a candidate adenovirus type 5-vectored vaccine encoding the receptor-binding domain of the SARS-CoV-2 spike protein (AdCOVID) induced robust immunity in both the airway mucosa and periphery, and completely protected K18-hACE2 mice from lethal SARS-CoV-2 challenge. Here we show that a single intranasal administration of AdCOVID limits viral replication in the nasal cavity of K18-hACE2 mice. AdCOVID also induces sterilizing immunity in the lungs of mice as reflected by the absence of infectious virus. Finally, AdCOVID prevents SARS-CoV-2 induced pathological damage in the lungs of mice. These data show that AdCOVID not only limits viral replication in the respiratory tract, but it also prevents virus-induced inflammation and immunopathology following SARS-CoV-2 infection.

Transmission of SARS-CoV-2 during indoor clubbing events: A clustered randomized, controlled, multicentre trial protocol

Introduction

The SARS-CoV-2 pandemic led to the implementation of several non-pharmaceutical interventions (NPIs), from closings of bars and restaurants to curfews and lockdowns. Vaccination campaigns started hoping it could efficiently alleviate NPI. The primary objective of the "Indoor Transmission of COVID-19" (ITOC) study is to determine among a fully vaccinated population the relative risk of SARS-CoV-2 transmission during one indoor clubbing event. Secondary objectives are to assess the transmission of other respiratory viruses, risk exposure, and attitudes toward COVID-19 vaccination, health pass, and psychological impact of indoor club closing.

Methods and analysis

Four thousand four hundred healthy volunteers aged 18-49 years and fully vaccinated will be included in Paris region. The intervention is an 8-hour indoor clubbing event with no masks, no social distance, maximum room capacity, and ventilation. A reservation group of up to 10 people will recruit participants, who will be randomized 1:1 to either the experimental group (2,200 volunteers in two venues with capacities of 1,000 people each) or the control group (2,200 volunteers asked not to go to the club). All participants will provide a salivary sample on the day of the experiment and 7 days later. They also will answer several questionnaires. Virological analyses include polymerase chain reaction (PCR) of salivary samples and air of the venue, investigating SARS-CoV-2 and 18 respiratory viruses.

Ethics and dissemination

Ethical clearance was first obtained in France from the institutional review board (Comité de Protection des Personnes Ile de France VII - CPP), and the trial received clearance from the French National Agency for Medicines and Health Products (Agence National de Sécurité du Médicament - ANSM). The trial is supported and approved by The Agence Nationale Recherche sur le SIDA, les hépatites et maladies émergences (ANRS-MIE). Positive, negative, and inconclusive results will be published in peer-reviewed scientific journals.

Trial registration number

IDR-CB 2021-A01473-38. Clinicaltrial.gov, identifier: NCT05311865.

Effects of covid-induced lockdown on inhabitants' perception of indoor air quality in naturally ventilated homes

The intensified indoor living during the spring 2020 lockdown, with enhanced user awareness of the prevailing conditions in their homes, constituted a natural stress test for the housing design in place today. Surveys conducted during this period have yielded lessons for designing better intervention strategies for the residential sector, taking into account the systematic morphological and economic limitations of the buildings concerned. These considerations should inform the development of policies and strategies for improving environmental quality compatible with lower residential energy consumption and higher quality of life. This study explores the effect of occupant behaviour on home ventilation and the perception of the impact of indoor air quality on user health before and during lockdown. The method deployed consisted in monitoring environmental variables and conducting user surveys before and after restrictions came into force. The findings showed that prior to lockdown, occupants were unaware of or paid little heed to changes in indoor air quality, failed to perceive stuffiness, and, as a rule, reported symptoms or discomfort only at night during the summer months. During lockdown, however, users came to attach greater importance to air quality, and a greater sensitivity to odours and a heightened awareness of CO2 concentration prompted them to ventilate their homes more frequently. In the spring of 2020, occupants also indicated a wider spectrum of indisposition, in particular in connection with sleep patterns.

The size and culturability of patient-generated SARS-CoV-2 aerosol

BACKGROUND

Aerosol transmission of COVID-19 is the subject of ongoing policy debate. Characterizing aerosol produced by people with COVID-19 is critical to understanding the role of aerosols in transmission.

OBJECTIVE

We investigated the presence of virus in size-fractioned aerosols from six COVID-19 patients admitted into mixed acuity wards in April of 2020.

METHODS

Size-fractionated aerosol samples and aerosol size distributions were collected from COVID-19 positive patients. Aerosol samples were analyzed for viral RNA, positive samples were cultured in Vero E6 cells. Serial RT-PCR of cells indicated samples where viral replication was likely occurring. Viral presence was also investigated by western blot and transmission electron microscopy (TEM).

RESULTS

SARS-CoV-2 RNA was detected by rRT-PCR in all samples. Three samples confidently indicated the presence of viral replication, all of which were from collected sub-micron aerosol. Western blot indicated the presence of viral proteins in all but one of these samples, and intact virions were observed by TEM in one sample.

SIGNIFICANCE

Observations of viral replication in the culture of submicron aerosol samples provides additional evidence that airborne transmission of COVID-19 is possible. These results support the use of efficient respiratory protection in both healthcare and by the public to limit transmission.

Goblet Cell Hyperplasia Increases SARS-CoV-2 Infection in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is one of the underlying conditions in adults of any age that place them at risk for developing severe illnesses associated with COVID-19. To determine whether SARS-CoV-2's cellular tropism plays a critical role in severe pathophysiology in the lung, we investigated its host cell entry receptor distribution in the bronchial airway epithelium of healthy adults and high-risk adults (those with COPD). We found that SARS-CoV-2 preferentially infects goblet cells in the bronchial airway epithelium, as mostly goblet cells harbor the entry receptor angiotensin-converting enzyme 2 (ACE2) and its cofactor transmembrane serine protease 2 (TMPRSS2). We also found that SARS-CoV-2 replication was substantially increased in the COPD bronchial airway epithelium, likely due to COPD-associated goblet cell hyperplasia. Likewise, SARS-CoV and Middle East respiratory syndrome (MERS-CoV) infection increased disease pathophysiology (e.g., syncytium formation) in the COPD bronchial airway epithelium. Our results reveal that goblet cells play a critical role in SARS-CoV-2-induced pathophysiology in the lung. IMPORTANCE SARS-CoV-2 or COVID-19's first case was discovered in December 2019 in Wuhan, China, and by March 2020 it was declared a pandemic by the WHO. It has been shown that various underlying conditions can increase the chance of having severe COVID-19. COPD, which is the third leading cause of death worldwide, is one of the conditions listed by the CDC which can increase the chance of severe COVID-19. The present study uses a healthy and COPD-derived bronchial airway epithelial model to study the COVID-19 and host factors which could explain the reason for COPD patients developing severe infection due to COVID-19.

Burden of Hospital-acquired SARS-CoV-2 Infections in Germany

Background

Avoiding in-hospital transmissions has been crucial in the COVID-19 pandemic. Little is known on the extent to which hospital-acquired SARS-CoV-2 variants have caused infections in Germany.

Aim

To analyse the occurrence and the outcomes of HAI with regard to different SARS-CoV-2 variants.

Methods

Patients with SARS-CoV-2 infections hospitalized between March 1^st, 2020 and May 17^th, 2022 in 79 hospitals of the Helios Group were included. Information on patients' characteristics and outcomes were retrieved from claims data. In accordance with the Robert Koch Institute, infections were classified as hospital-acquired when tested positive >6 days after admission and if no information hinted at a different source.

Findings

In all, 62,875 SARS-CoV-2 patients were analysed, of whom 10.6% had HAI. HAIs represented 14.7% of SARS-CoV-2 inpatients during the Wildtype period, 3.5% during Alpha (odds ratio: 0.21; 95% confidence interval: 0.19–0.24), 8.8% during Delta (2.70; 2.35–3.09) and 10.1% during Omicron (1.10; 1.03–1.19). When age and comorbidities were accounted for, HAI had lower odds for death than community-acquired infections (0.802; 0.740–0.866). Compared to the Wildtype period, HAIs during Omicron were associated with lower odds for ICU (0.78; 0.69–0.88), ventilation (0.47; 0.39–0.56), and death (0.33; 0.28–0.40).

Conclusion

Hospital-acquired SARS-CoV-2 infections occurred throughout the pandemic, affecting highly vulnerable patients. Although transmissibility increased with newer variants, the proportion of HAIs decreased, indicating improved infection prevention and/or the effect of immunization. Furthermore, the Omicron period was associated with improved outcomes. However, the burden of hospital-acquired SARS-CoV-2 infections remains high.

What were the historical reasons for the resistance to recognizing airborne transmission during the COVID-19 pandemic?

The question of whether SARS-CoV-2 is mainly transmitted by droplets or aerosols has been highly controversial. We sought to explain this controversy through a historical analysis of transmission research in other diseases. For most of human history, the dominant paradigm was that many diseases were carried by the air, often over long distances and in a phantasmagorical way. This miasmatic paradigm was challenged in the mid to late 19th century with the rise of germ theory, and as diseases such as cholera, puerperal fever, and malaria were found to actually transmit in other ways. Motivated by his views on the importance of contact/droplet infection, and the resistance he encountered from the remaining influence of miasma theory, prominent public health official Charles Chapin in 1910 helped initiate a successful paradigm shift, deeming airborne transmission most unlikely. This new paradigm became dominant. However, the lack of understanding of aerosols led to systematic errors in the interpretation of research evidence on transmission pathways. For the next five decades, airborne transmission was considered of negligible or minor importance for all major respiratory diseases, until a demonstration of airborne transmission of tuberculosis (which had been mistakenly thought to be transmitted by droplets) in 1962. The contact/droplet paradigm remained dominant, and only a few diseases were widely accepted as airborne before COVID-19: those that were clearly transmitted to people not in the same room. The acceleration of interdisciplinary research inspired by the COVID-19 pandemic has shown that airborne transmission is a major mode of transmission for this disease, and is likely to be significant for many respiratory infectious diseases.

Boundary conditions for exhaled airflow from a cough with a surgical or N95 mask

Wearing surgical or N95 masks is effective in reducing the infection risks of airborne infectious diseases. However, in the literature there are no detailed boundary conditions for airflow from a cough when a surgical or N95 mask is worn. These boundary conditions are essential for accurate prediction of exhaled particle dispersion by computational fluid dynamics (CFD). This study first constructed a coughing manikin with an exhalation system to simulate a cough from a person. The smoke visualization method was used to measure the airflow profile from a cough. To validate the setup of the coughing manikin, the results were compared with measured data from subject tests reported in the literature. The validated coughing manikin was then used to measure the airflow boundary conditions for a cough when a surgical mask was worn and when an N95 mask was worn, respectively. Finally, this study applied the developed airflow boundary conditions to calculate person-to-person particle transport from a cough when masks are worn. The calculated exhaled particle patterns agreed well with the smoke pattern in the visualization experiments. Furthermore, the calculated results indicated that, when the index person wore a surgical and a N95 mask, the total exposure of the receptor was reduced by 93.0% and 98.8%, respectively.

Detection of dental fomites using topical fluorescein

Background Thorough disinfection of dental facilities is of paramount importance during the COVID-19 pandemic. Patients, clinicians, students and nurses can all be infected by aerosols and dental droplets bearing COVID-19. However, droplets are transparent and often microscopic, so are difficult to detect in clinical practice.Methods To better understand the spread of dental droplets, we stained the dental irrigant with fluorescein and performed a series of procedures on a dental manikin. We then viewed droplets and fomite spread around the dental chair, with and without an ultraviolet (UV) light.Results Observations without the UV light showed minimal or no fluid spread. However, using UV light, we detected fluorescein on the dentist, chairs and the handpiece, as well as splatter on the floor and on the instrument tray. This was of educational value to the staff, who were reminded how far droplets had spread.Conclusion Fluorescein facilitates the detection of droplet spread and helps clinical staff to see high-risk areas that require in-depth cleaning. As clinical grade fluorescein is cheap and widely available, this technique may be useful for dental practices to train staff in the thorough decontamination of the clinical environment.

Trends in the Use of Face Coverings in Publicly Accessible Spaces During the COVID-19 Pandemic, King County, Washington, November 2020-May 2021

OBJECTIVES

Appropriate face covering use at public venues can help mitigate the transmission of SARS-CoV-2 in the absence of widespread vaccination and provide protection when viral variants become more infectious. The objective of this study was to evaluate compliance with a statewide face mask mandate by examining trends in face covering use in publicly accessible spaces in King County, Washington.

METHODS

From November 27, 2020, through May 11, 2021, we conducted a repeated cross-sectional observational study of face covering use across publicly accessible venues (eg, grocery and convenience stores, airport, transit center, post office). Trained observers recorded perceived sex, estimated age group, and face covering use. We calculated estimates of overall face covering use and prevalence ratios (PRs) with 95% CIs.

RESULTS

We observed 9865 people in 53 unique venues during 229 observation intervals during 6 observation periods. Correct face covering use was 87.2% overall and lowest at semi-outdoor venues such as transit hubs (78.1%) and the pick-up curb of Seattle-Tacoma International Airport (69.0%). Correct face covering use was lowest among men (PR = 1.42; 95% CI, 1.27-1.58) and among people aged 2-11 years (PR = 2.74; 95% CI, 2.37-3.17) and 12-17 years (PR = 1.36; 95% CI, 1.07-1.72). Compliance declined among adults aged ≥60 years and among younger age groups before vaccine eligibility.

CONCLUSIONS

Overall compliance with the statewide face mask mandate in King County was high. Layered mitigation strategies, including but not limited to the use of face coverings, and methods to assess adherence to them are crucial to preventing SARS-CoV-2 transmission.

A Tale of Three Recent Pandemics: Influenza, HIV and SARS-CoV-2

Emerging infectious diseases are one of the main threats to public health, with the potential to cause a pandemic when the infectious agent manages to spread globally. The first major pandemic to appear in the 20th century was the influenza pandemic of 1918, caused by the influenza A H1N1 strain that is characterized by a high fatality rate. Another major pandemic was caused by the human immunodeficiency virus (HIV), that started early in the 20th century and remained undetected until 1981. The ongoing HIV pandemic demonstrated a high mortality and morbidity rate, with discrepant impacts in different regions around the globe. The most recent major pandemic event, is the ongoing pandemic of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has caused over 5.7 million deaths since its emergence, 2 years ago. The aim of this work is to highlight the main determinants of the emergence, epidemic response and available countermeasures of these three pandemics, as we argue that such knowledge is paramount to prepare for the next pandemic. We analyse these pandemics’ historical and epidemiological contexts and the determinants of their emergence. Furthermore, we compare pharmaceutical and non-pharmaceutical interventions that have been used to slow down these three pandemics and zoom in on the technological advances that were made in the progress. Finally, we discuss the evolution of epidemiological modelling, that has become an essential tool to support public health policy making and discuss it in the context of these three pandemics. While these pandemics are caused by distinct viruses, that ignited in different time periods and in different regions of the globe, our work shows that many of the determinants of their emergence and countermeasures used to halt transmission were common. Therefore, it is important to further improve and optimize such approaches and adapt it to future threatening emerging infectious diseases.

TU Delft COVID-app: A tool to democratize CFD simulations for SARS-CoV-2 infection risk analysis

This work describes a modelling approach to SARS-CoV-2 dispersion based on experiments. The main goal is the development of an application integrated in Ansys Fluent to enable computational fluid dynamics (CFD) users to set up, in a relatively short time, complex simulations of virion-laden droplet dispersion for calculating the probability of SARS-CoV-2 infection in real life scenarios. The software application, referred to as TU Delft COVID-app, includes the modelling of human expiratory activities, unsteady and turbulent convection, droplet evaporation and thermal coupling. Data describing human expiratory activities have been obtained from selected studies involving measurements of the expelled droplets and the air flow during coughing, sneezing and breathing. Particle Image Velocimetry (PIV) measurements of the transient air flow expelled by a person while reciting a speech have been conducted with and without a surgical mask. The instantaneous velocity fields from PIV are used to determine the velocity flow rates used in the numerical simulations, while the average velocity fields are used for validation. Furthermore, the effect of surgical masks and N95 respirators on particle filtration and the probability of SARS-CoV-2 infection from a dose-response model have also been implemented in the application. Finally, the work includes a case-study of SARS-CoV-2 infection risk analysis during a conversation across a dining/meeting table that demonstrates the capability of the newly developed application.

A city-level analysis of PM2.5 pollution, climate and COVID-19 early spread in Spain

PURPUSE

The COVID-19 outbreak has escalated into the worse pandemic of the present century. The fast spread of the new SARS-CoV-2 coronavirus has caused devastating health and economic crises all over the world, with Spain being one of the worst affected countries in terms of confirmed COVID-19 cases and deaths per inhabitant. In this situation, the Spanish Government declared the lockdown of the country.

METHODS

The variations of air pollution in terms of fine particulate matter (PM_2.5) levels in seven representative cities of Spain are analyzed here considering the effect of meteorology during the national lockdown. The possible associations of PM_2.5 pollution and climate with COVID-19 accumulated cases were also analyzed.

RESULTS

While the epidemic curve was flattened, the results of the analysis show that the 4-week Spanish lockdown significantly reduced the PM_2.5 levels in only one city despite the drastically reduced human activity. Furthermore, no associations between either PM_2.5 exposure or environmental conditions and COVID-19 transmission were found during the early spread of the pandemic.

CONCLUSIONS

A longer period applying human activity restrictions is necessary in order to achieve significant reductions of PM_2.5 levels in all the analyzed cities. No effect of PM_2.5 pollution or weather on COVID-19 incidence was found for these pollutant levels and period of time.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-022-00786-2.

Layer-by-Layer Assembly of a Polysaccharide "Armor" on the Cell Surface Enabling the Prophylaxis of Virus Infection

Airborne pathogens, such as the world-spreading severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), cause global epidemics via transmission through the respiratory pathway. It is of great urgency to develop adequate interventions that can protect individuals against future pandemics. This study presents a nasal spray that forms a polysaccharide "armor" on the cell surface through the layer-by-layer self-assembly (LBL) method to minimize the risk of virus infection. The nasal spray has two separate components: chitosan and alginate. Harnessing the electrostatic interaction, inhaling the two polysaccharides alternatively enables the assembly of a barrier that reduces virus uptake into the cells. The results showed that this approach has no obvious cellular injury and endows cells with the ability to resist the infection of adenovirus and SARS-CoV-2 pseudovirus. Such a method can be a potential preventive strategy for protecting the respiratory tract against multiple viruses, especially the upcoming SARS-CoV-2 variants.

Aerosol capture and coronavirus spike protein deactivation by enzyme functionalized antiviral membranes

The airborne nature of coronavirus transmission makes it critical to develop new barrier technologies that can simultaneously reduce aerosol and viral spread. Here, we report nanostructured membranes with tunable thickness and porosity for filtering coronavirus-sized aerosols, combined with antiviral enzyme functionalization that can denature spike glycoproteins of the SARS-CoV-2 virus in low-hydration environments. Thin, asymmetric membranes with subtilisin enzyme and methacrylic functionalization show more than 98.90% filtration efficiency for 100-nm unfunctionalized and protein-functionalized polystyrene latex aerosol particles. Unfunctionalized membranes provided a protection factor of 540 ± 380 for coronavirus-sized particle, above the Occupational Safety and Health Administration's standard of 10 for N95 masks. SARS-CoV-2 spike glycoprotein on the surface of coronavirus-sized particles was denatured in 30 s by subtilisin enzyme-functionalized membranes with 0.02-0.2% water content on the membrane surface.

Identification of the source events for aerosol generation during oesophago-gastro-duodenoscopy

OBJECTIVE

To determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.

DESIGN

A prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient's mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.

RESULTS

Patients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L-1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L-1). Aerosol recording during OGD showed an average particle number concentration of 595 L-1 with a wide range (3-4320 L-1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient's reference voluntary coughs (11 710 vs 2320 L-1 and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.

CONCLUSION

Coughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens.

Characterizing observable COVID-19 controls in Pacific Northwest grocery stores

Utilizing a longitudinal, observational study, grocery store health and safety controls implemented during the COVID-19 pandemic across stores in two cities were characterized. Sixteen stores between Seattle, WA (n = 9) and Portland, OR (n = 7) were visited monthly by the study team from May 2020 to January 2021, and observations of controls were recorded using a standardized checklist in REDCap. The checklist included questions on the presence or absence of controls such as physical barriers, social distancing markers, required masking of customers, cleaning of check-out stands, and closures of store areas. Descriptive analyses were conducted to determine the proportion of stores with a certain control each month. Mixed-effects logistic regression was used to explore how controls changed over time, and whether differences were observed between cities or by income of the area the store serves. Source control (e.g., mask requirements) and engineering controls (e.g., physical barriers at checkout) were the most common and consistent controls observed across stores and over the study period. Controls such as having special hours for vulnerable populations, demarcations on aisles for directionality, and cleaning check-out stands between customers varied significantly over time (p < 0.05 in the mixed-effects model). Having an employee present to clean baskets and carts, as well as physical barriers between self-checkouts, were significantly more common in stores in areas above the median income (p < 0.05 in the mixed-effects model). To best protect workers and shoppers from infectious agents, controls should be evidence-based, consistently implemented across grocery stores, and coupled with administrative practices and policies to promote worker wellbeing.

Impact of population mixing between vaccinated and unvaccinated subpopulations on infectious disease dynamics: implications for SARS-CoV-2 transmission

Background:

The speed of vaccine development has been a singular achievement during the COVID-19 pandemic, although uptake has not been universal. Vaccine opponents often frame their opposition in terms of the rights of the unvaccinated. We sought to explore the impact of mixing of vaccinated and unvaccinated populations on risk of SARS-CoV-2 infection among vaccinated people.

Methods:

We constructed a simple susceptible–infectious–recovered compartmental model of a respiratory infectious disease with 2 connected subpopulations: people who were vaccinated and those who were unvaccinated. We simulated a spectrum of patterns of mixing between vaccinated and unvaccinated groups that ranged from random mixing to complete like-with-like mixing (complete assortativity), in which people have contact exclusively with others with the same vaccination status. We evaluated the dynamics of an epidemic within each subgroup and in the population as a whole.

Results:

We found that the risk of infection was markedly higher among unvaccinated people than among vaccinated people under all mixing assumptions. The contact-adjusted contribution of unvaccinated people to infection risk was disproportionate, with unvaccinated people contributing to infections among those who were vaccinated at a rate higher than would have been expected based on contact numbers alone. We found that as like-with-like mixing increased, attack rates among vaccinated people decreased from 15% to 10% (and increased from 62% to 79% among unvaccinated people), but the contact-adjusted contribution to risk among vaccinated people derived from contact with unvaccinated people increased.

Interpretation:

Although risk associated with avoiding vaccination during a virulent pandemic accrues chiefly to people who are unvaccinated, their choices affect risk of viral infection among those who are vaccinated in a manner that is disproportionate to the portion of unvaccinated people in the population.

Effects of location, classroom orientation, and air change rate on potential aerosol exposure: an experimental and computational study

This study examined the dispersion of potentially infectious aerosols in classrooms by means of both a CO₂ tracer gas, and multizone contaminant transport modeling. A total of 20 tests were conducted in three different university classrooms at multiple air change rates (4.4-9.7/h), each with two different room orientations: one with the tracer gas released from six student desks toward the air return, and one with the same tracer gas released away from it. Resulting tracer concentrations were measured by 19 different monitors arrayed throughout the room. Steady-state, mean tracer gas concentrations were calculated in six instructor zones (A-F) around the periphery of the room, with the results normalized by the concentration at the return, which was assumed to be representative of the well-mixed volume of the room. Across all classrooms, zones farthest from the return (C, D) had the lowest mean normalized concentrations (0.75), while those closest to the return (A, F) had the highest (0.95). This effect was consistent across room orientations (release both toward and away from the return), and air change rates. In addition, all zones around the periphery of the room had a significantly lower concentration than those adjacent to the sources. Increasing the ventilation rate reduced tracer gas concentrations significantly. Similar trends were observed via a novel approach to CONTAM modeling of the same rooms. These results indicate that informed selection of teaching location within the classroom could reduce instructor exposure.

Impact of natural ventilation on exposure to SARS-CoV 2 in indoor/semi-indoor terraces using CO2 concentrations as a proxy

Nowadays, it is necessary a better airborne transmission understanding of respiratory diseases in shared indoor and semi-indoor environments with natural ventilation in order to adopt effective people's health protection measures. The aim of this work is to evaluate the relative exposure to SARS-CoV 2 in a set of virtual scenarios representing enclosed and semi-enclosed terraces under different outdoor meteorological conditions. For this purpose, indoor CO₂ concentration is used as a proxy for the risk assessment. Airflow and people exhaled CO₂ in different scenarios are simulated through Computational Fluid Dynamics (CFD) modelling with Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach. Both spatial average concentrations and local concentrations are analyzed. In general, spatial average concentrations decrease as ventilation increases, however, depending on the people arrangement inside the terrace, spatial average concentrations and local concentrations can be very different. Therefore, for assessing the relative exposure to SARS-CoV 2 it is necessary to consider the indoor flow patterns between infectors and susceptibles. This research provides detailed information about CO₂ dispersion in enclosed/semi-enclosed scenarios, which can be very useful for reducing the transmission risk through better natural ventilation designs and improving the classic risk models since it allows to check their hypotheses in real-world scenarios. Although CFD ventilation studies in indoor/semi-indoor environments have been already addressed in the literature, this research is focused on restaurant terraces, scenarios scarcely investigated. Likewise, one of the novelties of this study is to take into account the outdoor meteorological conditions to appropriately simulate natural ventilation.

Disparities in COVID-19 fatalities among working Californians

BACKGROUND

Information on U.S. COVID-19 mortality rates by occupation is limited. We aimed to characterize 2020 COVID-19 fatalities among working Californians to inform preventive strategies.

METHODS

We identified laboratory-confirmed COVID-19 fatalities with dates of death in 2020 by matching death certificates to the state's COVID-19 case registry. Working status for decedents aged 18-64 years was determined from state employment records, death certificates, and case registry data and classified as "confirmed working," "likely working," or "not working." We calculated age-adjusted overall and occupation-specific COVID-19 mortality rates using 2019 American Community Survey denominators.

RESULTS

COVID-19 accounted for 8,050 (9.9%) of 81,468 fatalities among Californians 18-64 years old. Of these decedents, 2,486 (30.9%) were matched to state employment records and classified as "confirmed working." The remainder were classified as "likely working" (n = 4,121 [51.2%]) or "not working" (n = 1,443 [17.9%]) using death certificate and case registry data. Confirmed and likely working COVID-19 decedents were predominantly male (76.3%), Latino (68.7%), and foreign-born (59.6%), with high school or less education (67.9%); 7.8% were Black. The overall age-adjusted COVID-19 mortality rate was 30.0 per 100,000 workers (95% confidence interval [CI], 29.3-30.8). Workers in nine occupational groups had age-adjusted mortality rates higher than this overall rate, including those in farming (78.0; 95% CI, 68.7-88.2); material moving (77.8; 95% CI, 70.2-85.9); construction (62.4; 95% CI, 57.7-67.4); production (60.2; 95% CI, 55.7-65.0); and transportation (57.2; 95% CI, 52.2-62.5) occupations. While occupational differences in mortality were evident across demographic groups, mortality rates were three-fold higher for male compared with female workers and three- to seven-fold higher for Latino and Black workers compared with Asian and White workers.

CONCLUSION

Californians in manual labor and in-person service occupations experienced disproportionate COVID-19 mortality, with the highest rates observed among male, Latino, and Black workers; these occupational group should be prioritized for prevention.

Characterisation of Particle Size and Viability of SARS-CoV-2 Aerosols from a Range of Nebuliser Types Using a Novel Sampling Technique

Little is understood about the impact of nebulisation on the viability of SARS-CoV-2. In this study, a range of nebulisers with differing methods of aerosol generation were evaluated to determine SARS-CoV-2 viability following aerosolization. The aerosol particle size distribution was assessed using an aerosol particle sizer (APS) and SARS-CoV-2 viability was determined after collection into liquid media using All-Glass Impingers (AGI). Viable particles of SARS-CoV-2 were further characterised using the Collison 6-jet nebuliser in conjunction with novel sample techniques in an Andersen size-fractioning sampler to predict lung deposition profiles. Results demonstrate that all the tested nebulisers can generate stable, polydisperse aerosols (Geometric standard deviation (GSD) circa 1.8) in the respirable range (1.2 to 2.2 µm). Viable fractions (VF, units PFU/particle, the virus viability as a function of total particles produced) were circa 5 × 10^-3. VF and spray factors were not significantly affected by relative humidity, within this system where aerosols were in the spray tube an extremely short time. The novel Andersen sample collection methods successfully captured viable virus particles across all sizes; with most particle sizes below 3.3 µm. Particle sizes, in MMAD (Mass Median Aerodynamic Diameters), were calculated from linear regression of log₁₀-log₁₀ transformed cumulative PFU data, and calculated MMADs accorded well with APS measurements and did not differ across collection method types. These data will be vital in informing animal aerosol challenge models, and infection prevention and control policies.

Risk Stratification of SARS-CoV-2 Breakthrough Infections Based on an Outbreak at a Student Festive Event

In early 2022, the Coronavirus disease 2019 (COVID-19) remains a global challenge. COVID-19 is caused by an increasing number of variants of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Here, we report an outbreak of SARS-CoV-2 breakthrough infections related to a student festive event with 100 mostly vaccinated guests, which took place in Northern Bavaria, Germany, in October 2021. The data were obtained by retrospective guest interviews. In total, 95 students participated in the study, with 94 being fully vaccinated and 24 reporting infection by the delta variant. Correlation analyses among 15 examined variables revealed that time spent at the event, conversation with the supposed index person, and a homologous viral vector vaccination regime were significant risk factors for infection. Non-significant observations related to higher rates of infection included time since last vaccination, shared use of drinking vessels, and number of individual person-to-person contacts at the event. Our data suggest that a high rate of breakthrough infections with the delta variant occurs if no preventive measures are practiced. To limit infection risk, high-quality testing of participants should be considered a mandatory measure at gatherings, irrespective of the participants’ vaccination status.

Efficacy of Aerosol Reduction Measures for Dental Aerosol Generating Procedures

Aerosol particles generated by dental procedures could facilitate the transmission of infectious diseases and contain carcinogen particles. Such particles can penetrate common surgical masks and reach the lungs, leading to increased risk for dental care professionals. However, the risk of inhaling contaminated aerosol and the effectiveness of aerosol reduction measures in dental offices remain unclear. The present study aimed to quantify aerosols produced by drilling and scaling procedures and to evaluate present recommendations for aerosol reduction. The concentration of aerosol particles released from the mock scaling and drilling procedures on dental mannequin were measured using a TSI Optical Particle Sizer (OPS 3330) during 15-min sessions carried out in a single-patient examination room. Using a drilling procedure as the aerosol source, the aerosol reduction performance of two types of high-volume evacuators (HVEs) and a commercial off-the-shelf air purifier was evaluated in a simulated clinical setting. Using either HVEs or the air purifier individually reduced the aerosol accumulated over the course of a 15-minutes drilling procedure at a reduction rate of 94.8 to 97.6%. Using both measures simultaneously raised the reduction rate to 99.6%. The results show that existing HVEs can effectively reduce aerosol concentration generated by a drilling procedure and can be further improved by using an air purifier. Following current regulatory guidelines can ensure a low risk of inhaling contaminated aerosol for dentists, assistants, and patients.

Evaporation of liquid nanofilms: A minireview

Evaporation of virus-loaded droplets and liquid nanofilms plays a significant role in the pandemic of COVID-19. The evaporation mechanism of liquid nanofilms has attracted much attention in recent decades. In this minireview, we first introduce the relationship between the evaporation process of liquid nanofilms and the pandemic of COVID-19. Then, we briefly provide the frontiers of liquid droplet/nanofilm evaporation on solid surfaces. In addition, we discuss the potential application of machine learning in liquid nanofilm evaporation studies, which is expected to be helpful to build up a more accurate molecular model and to investigate the evaporation mechanism of liquid nanofilms on solid surfaces.

Face mask fit modifications that improve source control performance

BACKGROUND

During the COVID-19 pandemic, face masks are used as source control devices to reduce the expulsion of respiratory aerosols from infected people. Modifications such as mask braces, earloop straps, knotting and tucking, and double masking have been proposed to improve mask fit however the data on source control are limited.

METHODS

The effectiveness of mask fit modifications was determined by conducting fit tests on human subjects and simulator manikins and by performing simulated coughs and exhalations using a source control measurement system.

RESULTS

Medical masks without modification blocked ≥56% of cough aerosols and ≥42% of exhaled aerosols. Modifying fit by crossing the earloops or placing a bracket under the mask did not increase performance, while using earloop toggles, an earloop strap, and knotting and tucking the mask increased performance. The most effective modifications for improving source control performance were double masking and using a mask brace. Placing a cloth mask over a medical mask blocked ≥85% of cough aerosols and ≥91% of exhaled aerosols. Placing a brace over a medical mask blocked ≥95% of cough aerosols and ≥99% of exhaled aerosols.

CONCLUSIONS

Fit modifications can greatly improve the performance of face masks as source control devices for respiratory aerosols.

Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and Their Application to COVID-19 Outbreaks

Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (H_r) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.

An Emergency Powered Air-Purifying Respirator From Local Materials and its Efficacy Against Aerosolized Nanoparticles

We describe an approach used by a rural healthcare provider to convert surgical helmets into emergency powered air-purifying respirators (PAPRs) at the onset of the COVID-19 pandemic. The approach uses common materials and efficacy was demonstrated against aerosols measuring 7 nm to 25 μm in diameter.