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Loose-fitting powered air-purifying respirators (PAPRs) are a popular alternative to the use of filtering facepiece respirators for health care workers. Although PAPRs protect the wearer from aerosol particles, their ability to block infectious aerosol particles exhaled by the wearer from being released into the environment (called source control) is unclear. The source control performance of 4 PAPRs with loose-fitting facepieces were tested using a manikin that exhales aerosol particles. The PAPRs were tested by themselves and in combination with a face-worn product intended to provide source control (either a surgical mask or an N95 filtering facepiece respirator). Two PAPR facepieces with filtration panels significantly reduced the release of exhaled aerosols into the environment, while 3 facepieces without such panels did not. Wearing a surgical mask or respirator under the facepiece significantly improved the source control performance. Most PAPR facepieces do not block aerosols exhaled by the wearer. Facepieces designed to filter exhaled particles can prevent aerosols from being released into the environment. Wearing a surgical mask or a filtering facepiece respirator under the facepiece can also provide source control, but PAPRs are not typically certified for use with masks and respirators. [Display omitted] • Powered air-purifying respirators (PAPRs) provide respiratory protection. • PAPRs are a popular alternative to filtering facepiece respirators. • However, PAPRs typically do not block infectious aerosols expelled by the wearer. • A surgical mask or respirator worn under the PAPR can reduce aerosol expulsion. • PAPR facepieces designed to capture aerosols from the wearer can also be effective. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has highlighted the significant infection risks posed by aerosol-generating procedures (AGPs), such as intubation and cardiopulmonary resuscitation (CPR). Despite existing protective measures, high-risk environments like these require more effective safety solutions. In response, our research team has focused on developing a novel respiratory barrier enclosure designed to enhance the safety of healthcare workers and patients during AGPs. We developed a hood that covers the patient's respiratory area, incorporating a negative pressure system to contain aerosols. Using computational fluid dynamics (CFD) analysis, we optimized the hood's design and adjusted the negative pressure levels based on simulations of droplet dispersion. To test the design, Polyalphaolefin (PAO) particles were generated inside the hood, and leakage was measured every 10 s for 90 s. The open side of the hood was divided into nine sections for consistent leakage measurements, and a standardized structure was implemented to ensure accuracy. Our target was to maintain a leakage rate of less than 0.3%, in line with established filter-testing criteria. Through iterative improvements based on leakage rates and intubation efficiency, we achieved significant results. Despite reducing the hood's size, the redesigned enclosure showed a 36.2% reduction in leakage rates and an approximately 3204.6% increase in aerosol extraction efficiency in simulations. The modified hood, even in an open configuration, maintained a droplet leakage rate of less than 0.3%. These findings demonstrate the potential of a CFD-guided design in developing respiratory barriers that effectively reduce aerosol transmission risks during high-risk medical procedures. This approach not only improves the safety of both patients and healthcare providers but also provides a scalable solution for safer execution of AGPs in various healthcare settings. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spreads primarily through respiratory droplets, aerosols, and contaminated surfaces. While high-traffic locations like hospitals and airports have been studied extensively, detecting significant virus levels in aerosols and on environmental surfaces, campus settings remain underexplored. This study focused on two crowded buildings at the University of North Carolina at Charlotte (UNCC). From December 2021 to March 2022, we collected 16 indoor air samples and 201 samples from high-touch surfaces. During the sampling timeframe, 44.82% of surface samples from the Student Union and 28% from the University Recreational Center (UREC) tested positive for the presence of SARS-CoV-2 RNA. Median and average viral RNA copies per swab were higher in UREC (273 and 475) than in Student Union (92 and 269). However, all air samples tested negative. Surface positivity in these high-traffic campus locations was directly correlated with COVID-19 clinical cases in Mecklenburg County. The campus COVID-19 cases, driven by the Omicron wave, peaked a week before the peak detection of surface contamination. These findings underscore the importance of surface hygiene measures and highlight environmental conditions as potential contributors to COVID-19 spread on campuses.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spreads primarily through respiratory droplets, aerosols, and contaminated surfaces. While high-traffic locations like hospitals and airports have been studied extensively, detecting significant virus levels in aerosols and on environmental surfaces, campus settings remain underexplored. This study focused on two crowded buildings at the University of North Carolina at Charlotte (UNCC). From December 2021 to March 2022, we collected 16 indoor air samples and 201 samples from high-touch surfaces. During the sampling timeframe, 44.82% of surface samples from the Student Union and 28% from the University Recreational Center (UREC) tested positive for the presence of SARS-CoV-2 RNA. Median and average viral RNA copies per swab were higher in UREC (273 and 475) than in Student Union (92 and 269). However, all air samples tested negative. Surface positivity in these high-traffic campus locations was directly correlated with COVID-19 clinical cases in Mecklenburg County. The campus COVID-19 cases, driven by the Omicron wave, peaked a week before the peak detection of surface contamination. These findings underscore the importance of surface hygiene measures and highlight environmental conditions as potential contributors to COVID-19 spread on campuses. [ABSTRACT FROM AUTHOR]

The formation of a stress corrosion crack (SCC) in the canister wall of a dry cask storage system (DCSS) has been identified as a potential issue for the long-term storage of spent nuclear fuel. The presence of a SCC in a storage system could represent a through-wall flow path from the canister interior to the environment. Modern, vertical DCSSs are of particular interest due to the commercial practice of using relatively high helium backfill pressures (up to approximately 800 kPa) in the canister to enhance internal natural convection. This pressure differential offers a comparatively high driving potential for blowdown of any particulates that might be present in the canister in the event of a through-wall SCC. In this study, the rates of gas flow and aerosol transmission of a spent fuel surrogate through an engineered microchannel with dimensions representative of a SCC were evaluated experimentally using coupled mass flow and aerosol analyzers. The microchannel was formed by mating two gauge blocks with a linearly tapering slot orifice nominally 13 μm (0.0005 in.) tall on the upstream side and 25 μm (0.001 in.) tall on the downstream side. The orifice is 12.7 mm (0.500 in.) wide by 8.89 mm (0.350 in.) long (flow length). Surrogate aerosols of cerium oxide (CeO2) were seeded and mixed with either helium or air inside a pressurized tank. The aerosol characteristics were measured immediately upstream and downstream of the simulated SCC at elevated and ambient pressures, respectively. The next iteration of testing involves replacing the engineered microchannel with lab-grown SCCs. Preliminary clean flow testing has been conducted on SCC samples provided by the Electric Power Research Institute. These data sets demonstrate a new capability to characterize SCCs under well-controlled boundary conditions. Preliminary testing efforts are focused on understanding the evolution in both the size and quantity of a hypothetical release of aerosolized spent fuel particles from failed fuel cladding into the canister interior, and ultimately, through a SCC. [ABSTRACT FROM AUTHOR]

Virus seasonality is affected by many environmental factors. UV radiation is a less studied but potentially important factor in virus outdoor aerosol transmission. Virus aerosol transmission in an Arctic environment was simulated by nebulizing Phi6 outdoors to study longer range (0-75 m) transmission. Aerosolized viruses were collected using host-containing agar plates, Biosamplers and filter collectors. Additionally, the effects of long-term exposure to solar UV radiation were studied on Phi6 and its host bacteria Pseudomonas phaseolicola. Phi6 remained infectious in aerosols for at least 50 m outdoors, however, potential for longer transmission distance still exists. Exposure to solar UV radiation did not significantly affect Phi6 viability, however, a decreasing trend was seen over an 8 h exposure time. Potential UV radiation related damages were found in the host bacteria's genome, but not in Phi6. This study shows that some viruses can remain infectious and travel for relatively long distances outdoors. Solar UV radiation was found to have minimal or no effect on Phi6 aerosol transmission at these distances, however, Phi6 is known to be resilient against UV radiation. Further studies are required with longer distance collection to understand the full potential of virus aerosol transmission outdoors. Additionally, other model viruses should be experimented with to understand how different viruses remain infectious in aerosols.

Corona virus disease 2019 (COVID-19) has exerted a profound adverse impact on human health. Studies have demonstrated that aerosol transmission is one of the major transmission routes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Pathogenic microorganisms such as SARS-CoV-2 can survive in the air and cause widespread infection among people. Early monitoring of pathogenic microorganism transmission in the atmosphere and accurate epidemic prediction are the frontier guarantee for preventing large-scale epidemic outbreaks. Monitoring of pathogenic microorganisms in the air, especially in densely populated areas, may raise the possibility to detect viruses before people are widely infected and contain the epidemic at an earlier stage. The multi-scale coupled accurate epidemic prediction system can provide support for governments to analyze the epidemic situation, allocate health resources, and formulate epidemic response policies. This review first elaborates on the effects of the atmospheric environment on pathogenic microorganism transmission, which lays a theoretical foundation for the monitoring and prediction of epidemic development. Secondly, the monitoring technique development and the necessity of monitoring pathogenic microorganisms in the atmosphere are summarized and emphasized. Subsequently, this review introduces the major epidemic prediction methods and highlights the significance to realize a multi-scale coupled epidemic prediction system by strengthening the multidisciplinary cooperation of epidemiology, atmospheric sciences, environmental sciences, sociology, demography, etc. By summarizing the achievements and challenges in monitoring and prediction of pathogenic microorganism transmission in the atmosphere, this review proposes suggestions for epidemic response, namely, the establishment of an integrated monitoring and prediction platform for pathogenic microorganism transmission in the atmosphere.

Summary: We investigate the transmission of aerosol particles in an airplane cabin with a joint approach using experiments and simulation. Experiments were conducted in a realistic aircraft cabin with heated dummies acting as passengers. A Sheffield head with an aerosol generator was used to emulate an infected passenger and particle numbers were measured at different locations throughout the cabin to quantify the exposure of other passengers. The same setting was simulated with a computational fluid dynamics model consisting of a Lagrange continuous phase for capturing the air flow, coupled with a Lagrange suspended discrete phase to represent the aerosols. Virtual measurements were derived from the simulation and compared with the experiments. Our main results are: the experimental setup provides good measurements well suited for model validation, the simulation does correctly reproduce the fundamental mechanisms of aerosol dispersion and simulations can help to improve the understanding of aerosol transmission for example by visualizing particle distributions. Furthermore, with findings from the simulation it was possible to crucially improve the experimental setup, proving that feedback between the numerical and the hardware world is indeed beneficial. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has highlighted the significant infection risks posed by aerosol-generating procedures (AGPs), such as intubation and cardiopulmonary resuscitation (CPR). Despite existing protective measures, high-risk environments like these require more effective safety solutions. In response, our research team has focused on developing a novel respiratory barrier enclosure designed to enhance the safety of healthcare workers and patients during AGPs. We developed a hood that covers the patient’s respiratory area, incorporating a negative pressure system to contain aerosols. Using computational fluid dynamics (CFD) analysis, we optimized the hood’s design and adjusted the negative pressure levels based on simulations of droplet dispersion. To test the design, Polyalphaolefin (PAO) particles were generated inside the hood, and leakage was measured every 10 s for 90 s. The open side of the hood was divided into nine sections for consistent leakage measurements, and a standardized structure was implemented to ensure accuracy. Our target was to maintain a leakage rate of less than 0.3%, in line with established filter-testing criteria. Through iterative improvements based on leakage rates and intubation efficiency, we achieved significant results. Despite reducing the hood’s size, the redesigned enclosure showed a 36.2% reduction in leakage rates and an approximately 3204.6% increase in aerosol extraction efficiency in simulations. The modified hood, even in an open configuration, maintained a droplet leakage rate of less than 0.3%. These findings demonstrate the potential of a CFD-guided design in developing respiratory barriers that effectively reduce aerosol transmission risks during high-risk medical procedures. This approach not only improves the safety of both patients and healthcare providers but also provides a scalable solution for safer execution of AGPs in various healthcare settings.

It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow, measured in air change per hour (ACH). However, increasing ACH did not effectively prevent the spread of COVID-19. To better understand the role of ACH and airflow large-scale patterns, a comprehensive fully transient computational fluid dynamics (CFD) simulation of two-phase flows based on a discrete phase model (DPM) was performed in a university classroom setting with people present. The investigations encompass various particle sizes, ventilation layouts, and flow rates. The findings demonstrated that the particle size threshold at which particles are deemed airborne is highly influenced by the background flow strength and large-scale flow pattern, ranging from 5 µm to 10 µm in the cases investigated. The effects of occupants are significant and must be precisely accounted for in respiratory particle transport studies. An enhanced ventilation design (UFAD-CDR) for university classrooms is introduced that places a premium on mitigating airborne disease spread. Compared to the baseline design at the same ACH, this design successfully reduced the maximum number density of respiratory particles by up to 85%. A novel airflow-related parameter, Horizontality, is introduced to quantify and connect the large-scale airflow pattern with indoor aerosol transport. This underscores that ACH alone cannot ensure or regulate air quality. In addition to the necessary ACH for air exchange, minimizing horizontal bulk motion is essential for reducing aerosol transmissibility within the room. [ABSTRACT FROM AUTHOR]

There is an urgent need for stronger protection from aerosol-transmissible diseases in healthcare settings—for workers, patients, volunteers, and visitors. Concerned that the Centers for Disease Control and Prevention (CDC) Healthcare Infection Control Practices Advisory Committee (HICPAC) lacks diversity in expertise and experience and has not consulted widely with all concerned parties regarding a planned update to the 2007 Guideline for Isolation Precautions, a workshop was developed to consider the science and lessons learned before and during the COVID-19 pandemic. Sponsored by the New York/New Jersey Occupational Safety and Health Center, Preventing Aerosol-Transmissible Diseases in Healthcare Settings: The Need for Protective Guidelines and Standards was held on October 13, 2023, with these goals: describe current CDC/HICPAC infection prevention guidelines, review current scientific understanding of aerosol-transmissible pathogens, and consider perspectives from a wide range of groups currently excluded from the CDC HICPAC process. [ABSTRACT FROM AUTHOR]

This review examines the risk of infection transmission in dental settings through aerosols, particularly in light of the COVID-19 pandemic. Dental procedures, particularly those involving highspeed instruments, produce aerosols containing saliva, blood, and microbes. These aerosols pose a significant risk of transmission, especially in close contact situations. Measures such as highvolume evacuation, barrier protection (masks, gloves, eye protection), and preprocedural rinses with antiseptic mouthwash can help reduce aerosol contamination. However, the effectiveness of these measures varies, and more research is needed to fully understand and mitigate the risk. The review also discusses the legal and regulatory considerations surrounding aerosol contamination in dental practices. Ultimately, adherence to recommended protocols from organizations like the CDC and ADA is crucial for minimizing aerosol-related infection transmission in dental settings, particularly in the context of the ongoing COVID-19 pandemic. [ABSTRACT FROM AUTHOR]

Introduction: The rubber dam plays an important role in isolation of teeth during dental procedures and helps prevent contamination risks. The usage of rubber dam in day-to-day clinical practice has become crucial during the pandemic. Aim: To assess the knowledge, attitudes, and practices of rubber dam usage among dental practitioners in India during and after the Coronavirus Disease 2019 (COVID-19) pandemic. Materials and Methods: This was a cross-sectional surveybased examination. A pretested 15-item questionnaire was administered to 300 dental practitioners in Tamil Nadu, India, using Google Forms. The questions were categorised into three parameters: knowledge, attitude, and practice. The study population included dentists of all types who were performing restorative and endodontic procedures. Information was collected regarding age, gender, educational qualification, and the use of rubber dam. The questionnaire contained leading questions designed to assess the opinions and attitudes of dentists toward the use of rubber dam. The responses received were statistically analysed using the Chi-square test. Results: Out of the respondents, 257 (85.66%) reported being taught about rubber dam placement, while 43 (14.33%) were unaware of its usage. Prior to the pandemic, 181 (61.35%) of respondents were utilising rubber dam for conservative and endodontic procedures. Only 151 (50.84%) of practitioners believed that rubber dam placement prevents aerosol transmission. Additionally, 266 (89.26%) of respondents expressed willingness to learn and gain knowledge about rubber dam. Conclusion: The study concluded that dental practitioners exhibited a positive attitude towards incorporating rubber dam usage in their practice and showed willingness to update their knowledge about rubber dam, regardless of age, due to the pandemic.

An integrated computational fluid dynamics (CFD) model was developed to simulate aerosol transmission of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) from a source to recipient building using a previously published experimental study as a test case. The integrated model consisted of CFD simulations of PRRSV aerosol movement in the atmosphere and within the recipient building, viral infectivity decay, and infection dose-response. Specific hours with the appropriate wind direction during two days (June 6 and 7, 2006) were simulated, based on historical weather data. For a given airborne PRRSV concentration exhausted from the source building, the model predicted the PRRSV distribution, infectivity decay, and probability of infection in the recipient building. Simulations indicated that wind affected the aerosol entry into the recipient building, with more stable and continuous aerosol entry at lower wind speed conditions on June 7. Elevated aerosol and PRRSV concentrations on June 7 resulted in pigs being exposed to higher doses of PRRSV than on June 6, but this only made a difference in probability of infection when there was a moderate level of PRRSV (500 TCID m−3) exhausted from the source building. At this level, there was a difference in exposure dose for pigs at different locations (pens). Overall, the positive PRRSV air sample on the morning of June 7 in the previously reported experimental study confirmed the adequacy of the model simulations, which predicted the aerosol transmission event that infected pigs in the recipient building was likely to have occurred on June 7, 2006. • Model simulates aerosol transmission of animal diseases between buildings. • Model integrates CFD with infectivity decay and dose-response for PRRS virus in pigs. • Model able to account for virus levels in infected building and wind conditions. • Model adequately predicted infection probability in a neighbouring building. [ABSTRACT FROM AUTHOR]

Introduction: The rubber dam plays an important role in isolation of teeth during dental procedures and helps prevent contamination risks. The usage of rubber dam in day-to-day clinical practice has become crucial during the pandemic. Aim: To assess the knowledge, attitudes, and practices of rubber dam usage among dental practitioners in India during and after the Coronavirus Disease 2019 (COVID-19) pandemic. Materials and Methods: This was a cross-sectional survey-based examination. A pretested 15-item questionnaire was administered to 300 dental practitioners in Tamil Nadu, India, using Google Forms. The questions were categorised into three parameters: knowledge, attitude, and practice. The study population included dentists of all types who were performing restorative and endodontic procedures. Information was collected regarding age, gender, educational qualification, and the use of rubber dam. The questionnaire contained leading questions designed to assess the opinions and attitudes of dentists toward the use of rubber dam. The responses received were statistically analysed using the Chi-square test. Results: Out of the respondents, 257 (85.66%) reported being taught about rubber dam placement, while 43 (14.33%) were unaware of its usage. Prior to the pandemic, 181 (61.35%) of respondents were utilising rubber dam for conservative and endodontic procedures. Only 151 (50.84%) of practitioners believed that rubber dam placement prevents aerosol transmission. Additionally, 266 (89.26%) of respondents expressed willingness to learn and gain knowledge about rubber dam. Conclusion: The study concluded that dental practitioners exhibited a positive attitude towards incorporating rubber dam usage in their practice and showed willingness to update their knowledge about rubber dam, regardless of age, due to the pandemic. [ABSTRACT FROM AUTHOR]

A study of the aerodynamic characteristics of aerosol expiration is important for understanding the size distribution of droplet concentration in COVID-19 disease transmission. This study measured the initial concentration and size distribution of droplets released during four breathing processes: nose breathing, mouth breathing, reading alphabets and counting numbers. Influencing factors on droplet generation were studied by statistical analyses. Significant differences in droplet concentration among the four breathing activities in pairs were found (p < 0.001), except for reading alphabets and numbers (p = 1). The droplet concentration during nose breathing (p < 0.05), but not mouth breathing (p = 0.136), of male subjects, was found significantly higher than that of female subjects. The droplet concentration generated by speaking during letters reading with special phonemes, for example, /i:/, was significantly (p < 0.05) higher than reading letters without phonemes. The discharged droplet sizes from four breathing activities were dominated by small droplets (d p < 1.037 μm of over 50% and d p < 2.642 μm of over 80%). Basically, no particles larger than 8 μm were detected by the aerodynamic particle sizer. The inference indicates a possible aerosol transmission of disease during non-symptomatic aerosol-producing activities such as breathing or speaking and may elucidate the disease transmission pathway of COVID-19. [ABSTRACT FROM AUTHOR]

On July 20, 2023 a letter was sent to the Director of the Centers for Disease Control and Prevention requesting the agency's Healthcare Infection Control Practice Advisory Committee seek input from more stakeholders and the public, recognize the importance of infectious disease transmission by inhalation of human-generated aerosols, and ensure the application of interventions from all levels of the control hierarchy. [ABSTRACT FROM AUTHOR]

During the recent pandemic of COVID-19 (SARS-CoV-2), influential public health agencies such as the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have favored the view that SARS CoV-2 spreads predominantly via droplets. Many experts in aerobiology have openly opposed that stance, forcing a vigorous debate on the topic. In this review, we discuss the various proposed modes of viral transmission, stressing the interdependencies between droplet, aerosol, and fomite spread. Relative humidity and temperature prevailing determine the rates at which respiratory aerosols and droplets emitted from an expiratory event (sneezing, coughing, etc.) evaporate to form smaller droplets or aerosols, or experience hygroscopic growth. Gravitational settling of droplets may result in contamination of environmental surfaces (fomites). Depending upon human, animal and mechanical activities in the occupied space indoors, viruses deposited on environmental surfaces may be re-aerosolized (re-suspended) to contribute to aerosols, and can be conveyed on aerial particulate matter such as dust and allergens. The transmission of respiratory viruses may then best be viewed as resulting from dynamic virus spread from infected individuals to susceptible individuals by various physical states of active respiratory emissions, instead of the current paradigm that emphasizes separate dissemination by respiratory droplets, aerosols or by contaminated fomites. To achieve the optimum outcome in terms of risk mitigation and infection prevention and control (IPAC) during seasonal infection peaks, outbreaks, and pandemics, this holistic view emphasizes the importance of dealing with all interdependent transmission modalities, rather than focusing on one modality. [ABSTRACT FROM AUTHOR]

Abstract Background The emergence of an unprecedented novel severe acute respiratory syndrome coronavirus-2 (SARS-C0V-2), which causes the coronavirus disease 2019 (COVID-19) pandemic, has created new scenarios in basic life support (BLS) management. According to current evidence, SARS-CoV-2 can be transmitted airborne in aerosol particles during resuscitation. Research evidence found an alarming global increase in out-of-hospital cardiac arrests during the COVID-19 pandemic. Healthcare providers are legally obliged to respond to cardiac arrest as soon as possible. Chiropractors will likely encounter potential exercise-related and non-exercise-related cardiac emergencies at some point in their professional lives. They have a duty of care to respond to emergencies such as cardiac arrest. Chiropractors are increasingly involved in providing care, including emergency care, for athletes and spectators at sporting events. Also, exercise-related cardiac arrest in adult patients may occur during exercise testing or rehabilitation with exercise prescriptions in chiropractic and other healthcare settings. Little is known about the COVID-19 BLS guidelines for chiropractors. Knowledge of the current COVID-19-specific adult BLS guidelines is essential to developing an emergency response plan for the on-field and sideline management of exercise-related cardiac arrest and non-athletic, non-exercise-related cardiac arrest. Main text Seven peer-reviewed articles on the COVID-19-specific BLS guidelines, including two updates, were reviewed for this commentary. Responding to the COVID-19 pandemic, the national and international resuscitation organizations recommended interim COVID-19-specific BLS guidelines with precaution, resuscitation, and education strategies. BLS safety is paramount. A precautionary approach with the bare minimum of appropriate personal protective equipment for resuscitation is recommended. There was disagreement among the COVID-19 BLS guidelines on the level of personal protective equipment. All healthcare professionals should also undergo self-directed BLS e-learning and virtual skill e-training. The summarized COVID-19-specific adult BLS guideline strategies and protocols are tabled, respectively. Conclusions This commentary provides a practical overview and highlights current evidence-based intervention strategies of the COVID-19-specific adult BLS guidelines that may help chiropractors and other healthcare providers reduce BLS-related exposures to SARS-CoV-2 and the risks of SARS-CoV-2 transmission and maximize the efficacy of resuscitation. This study is relevant to and impacts future COVID-19-related research in areas such as infection prevention and control.

Objectives: As the world transitions to COVID-19 endemicity, studies focusing on aerosol shedding of highly transmissible SARS-CoV-2 variants of concern (VOCs) are vital for the calibration of infection control measures against VOCs that are likely to circulate seasonally. This follow-up Gesundheit-II aerosol sampling study aims to compare the aerosol shedding patterns of Omicron VOC samples with pre-Omicron variants analyzed in our previous study. Design: Coarse and fine aerosol samples from 47 patients infected with SARS-CoV-2 were collected during various respiratory activities (passive breathing, talking, and singing) and analyzed using reverse transcription-quantitative polymerase chain reaction and virus culture. Results: Compared with patients infected with pre-Omicron variants, comparable SARS-CoV-2 RNA copy numbers were detectable in aerosol samples of patients infected with Omicron despite being fully vaccinated. Patients infected with Omicron also showed a slight increase in viral aerosol shedding during breathing activities and were more likely to have persistent aerosol shedding beyond 7 days after disease onset. Conclusion: This follow-up study reaffirms the aerosol shedding properties of Omicron and should guide continued layering of public health interventions even in highly vaccinated populations.

The COVID-19 pandemic has had a profound impact on human society. The isolation of SARS-CoV-2 from patients' feces on human cell line raised concerns of possible transmission through human feces including exposure to aerosols generated by toilet flushing and through the indoor drainage system. Currently, routes of transmission, other than the close contact droplet transmission, are still not well understood. A quantitative microbial risk assessment was conducted to estimate the health risks associated with two aerosol exposure scenarios: 1) toilet flushing, and 2) faulty connection of a floor drain with the building's main sewer pipe. SARS-CoV-2 data were collected from the emerging literature. The infectivity of the virus in feces was estimated based on a range of assumption between viral genome equivalence and infectious unit. The human exposure dose was calculated using Monte Carlo simulation of viral concentrations in aerosols under each scenario and human breathing rates. The probability of COVID-19 illness was generated using the dose-response model for SARS-CoV-1, a close relative of SARS-CoV-2, that was responsible for the SARS outbreak in 2003. The results indicate the median risks of developing COVID-19 for a single day exposure is 1.11 × 10-10 and 3.52 × 10-11 for toilet flushing and faulty drain scenario, respectively. The worst case scenario predicted the high end of COVID-19 risk for the toilet flushing scenario was 5.78 × 10-4 (at 95th percentile). The infectious viral loads in human feces are the most sensitive input parameter and contribute significantly to model uncertainty.

During the 2020 COVID-19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID-19 and two died. Transmission by the aerosol route is likely; it appears unlikely that either fomite or ballistic droplet transmission could explain a substantial fraction of the cases. It is vital to identify features of cases such as this to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was dominated by inhalation of respiratory aerosol generated by one index case, we use the available evidence to infer the emission rate of aerosol infectious quanta. We explore how the risk of infection would vary with several influential factors: ventilation rate, duration of event, and deposition onto surfaces. The results indicate a best-estimate emission rate of 970 ± 390 quanta/h. Infection risk would be reduced by a factor of two by increasing the aerosol loss rate to 5 h-1 and shortening the event duration from 2.5 to 1 h.

During the recent pandemic of COVID-19 (SARS-CoV-2), influential public health agencies such as the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have favored the view that SARS CoV-2 spreads predominantly via droplets. Many experts in aerobiology have openly opposed that stance, forcing a vigorous debate on the topic. In this review, we discuss the various proposed modes of viral transmission, stressing the interdependencies between droplet, aerosol, and fomite spread. Relative humidity and temperature prevailing determine the rates at which respiratory aerosols and droplets emitted from an expiratory event (sneezing, coughing, etc.) evaporate to form smaller droplets or aerosols, or experience hygroscopic growth. Gravitational settling of droplets may result in contamination of environmental surfaces (fomites). Depending upon human, animal and mechanical activities in the occupied space indoors, viruses deposited on environmental surfaces may be re-aerosolized (re-suspended) to contribute to aerosols, and can be conveyed on aerial particulate matter such as dust and allergens. The transmission of respiratory viruses may then best be viewed as resulting from dynamic virus spread from infected individuals to susceptible individuals by various physical states of active respiratory emissions, instead of the current paradigm that emphasizes separate dissemination by respiratory droplets, aerosols or by contaminated fomites. To achieve the optimum outcome in terms of risk mitigation and infection prevention and control (IPAC) during seasonal infection peaks, outbreaks, and pandemics, this holistic view emphasizes the importance of dealing with all interdependent transmission modalities, rather than focusing on one modality.

Although it is well established that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be transmitted through aerosols, the mode of long-range aerosol transmission in high-rise buildings remains unclear. In this study, we analyzed an outbreak of coronavirus disease 2019 (COVID-19) that occurred in a high-rise building in China. Our objective was to investigate the plausibility of aerosol transmission of SARS-CoV-2 by testing relevant environmental variables and measuring the dispersion of a tracer gas in the drainage system of the building. The outbreak involved 7 infected families, of which 6 were from vertically aligned flats on different floors. Environmenìtal data revealed that 3 families' bathrooms were contaminated by SARS-CoV-2. In our tracer experiment, we injected tracer gas (CO2) into the dry floor drains and into water-filled toilets in the index case' s bathroom. Our findings showed that the gas could travel through vertical pipes by the dry floor drains, but not through the water of the toilets. This indicates that dry floor drains might facilitate the transmission of viral aerosols through the sewage system. On the basis of circumstantial evidence, long-range aerosol transmission may have contributed to the community outbreak of COVID-19 in this high-rise building. The vertical transmission of diseases through aerosols in high-rise buildings demands urgent attention. [ABSTRACT FROM AUTHOR]

We investigated a cluster of SARS-CoV-2 infections in a quarantine hotel in Taiwan in December 2021. The cluster involved 3 case patients who lived in nonadjacent rooms on different floors. They had no direct contact during their stay. By direct exploration of the space above the room ceilings, we found residual tunnels, wall defects, and truncated pipes between their rooms. We conducted a simplified tracer-gas experiment to assess the interconnection between rooms. Aerosol transmission through structural defects in floors and walls in this poorly ventilated hotel was the most likely route of virus transmission. This event demonstrates the high transmissibility of Omicron variants, even across rooms and floors, through structural defects. Our findings emphasize the importance of ventilation and integrity of building structure in quarantine facilities.

Background: The emergence of an unprecedented novel severe acute respiratory syndrome coronavirus-2 (SARS-C0V-2), which causes the coronavirus disease 2019 (COVID-19) pandemic, has created new scenarios in basic life support (BLS) management. According to current evidence, SARS-CoV-2 can be transmitted airborne in aerosol particles during resuscitation. Research evidence found an alarming global increase in out-of-hospital cardiac arrests during the COVID-19 pandemic. Healthcare providers are legally obliged to respond to cardiac arrest as soon as possible. Chiropractors will likely encounter potential exercise-related and non-exercise-related cardiac emergencies at some point in their professional lives. They have a duty of care to respond to emergencies such as cardiac arrest. Chiropractors are increasingly involved in providing care, including emergency care, for athletes and spectators at sporting events. Also, exercise-related cardiac arrest in adult patients may occur during exercise testing or rehabilitation with exercise prescriptions in chiropractic and other healthcare settings. Little is known about the COVID-19 BLS guidelines for chiropractors. Knowledge of the current COVID-19-specific adult BLS guidelines is essential to developing an emergency response plan for the on-field and sideline management of exercise-related cardiac arrest and non-athletic, non-exercise-related cardiac arrest. Main text: Seven peer-reviewed articles on the COVID-19-specific BLS guidelines, including two updates, were reviewed for this commentary. Responding to the COVID-19 pandemic, the national and international resuscitation organizations recommended interim COVID-19-specific BLS guidelines with precaution, resuscitation, and education strategies. BLS safety is paramount. A precautionary approach with the bare minimum of appropriate personal protective equipment for resuscitation is recommended. There was disagreement among the COVID-19 BLS guidelines on the level of personal protective equipment. All healthcare professionals should also undergo self-directed BLS e-learning and virtual skill e-training. The summarized COVID-19-specific adult BLS guideline strategies and protocols are tabled, respectively. Conclusions: This commentary provides a practical overview and highlights current evidence-based intervention strategies of the COVID-19-specific adult BLS guidelines that may help chiropractors and other healthcare providers reduce BLS-related exposures to SARS-CoV-2 and the risks of SARS-CoV-2 transmission and maximize the efficacy of resuscitation. This study is relevant to and impacts future COVID-19-related research in areas such as infection prevention and control. [ABSTRACT FROM AUTHOR]

• We compared the SARS-CoV-2 Omicron variant aerosol shedding with earlier variants. • Despite vaccination, the shedding of a patient infected with Omicron is comparable to the shedding of a patient infected with pre-Omicron variants. • Patients infected with Omicron shed higher SARS-CoV-2 levels during passive breathing. • The aerosol shedding of a patient infected with Omicron lasted longer after the disease onset. As the world transitions to COVID-19 endemicity, studies focusing on aerosol shedding of highly transmissible SARS-CoV-2 variants of concern (VOCs) are vital for the calibration of infection control measures against VOCs that are likely to circulate seasonally. This follow-up Gesundheit-II aerosol sampling study aims to compare the aerosol shedding patterns of Omicron VOC samples with pre-Omicron variants analyzed in our previous study. Coarse and fine aerosol samples from 47 patients infected with SARS-CoV-2 were collected during various respiratory activities (passive breathing, talking, and singing) and analyzed using reverse transcription-quantitative polymerase chain reaction and virus culture. Compared with patients infected with pre-Omicron variants, comparable SARS-CoV-2 RNA copy numbers were detectable in aerosol samples of patients infected with Omicron despite being fully vaccinated. Patients infected with Omicron also showed a slight increase in viral aerosol shedding during breathing activities and were more likely to have persistent aerosol shedding beyond 7 days after disease onset. This follow-up study reaffirms the aerosol shedding properties of Omicron and should guide continued layering of public health interventions even in highly vaccinated populations. [Display omitted] [ABSTRACT FROM AUTHOR]

The risk of COVID-19 infection from virulent aerosols is particularly high indoors. This is especially true for classrooms, which often do not have pre-installed ventilation and are occupied by a large number of students at the same time. It has been found that precautionary measures, such as the use of air purifiers (AP), physical distancing, and the wearing of masks, can reduce the risk of infection. To quantify the actual effect of precautions, it is not possible in experimental studies to expose subjects to virulent aerosols. Therefore, in this study, we develop a computational fluid dynamics (CFD) model to evaluate the impact of applying the aforementioned precautions in classrooms on reducing aerosol concentration and potential exposure in the presence of index or infected patients. A CFD-coupled Wells–Riley model is used to quantify the infection probability (IP) in the presence of index patients. Different cases are simulated by varying the occupancy of the room (half/full), the volumetric flow rate of the AP, two different locations of the AP, and the effect of wearing masks. The results suggest that using an AP reduces the spread of virulent aerosols and thereby reduces the risk of infection. However, the risk of the person sitting adjacent to the index patient is only marginally reduced and can be avoided with the half capacity of the class (physical distancing method) or by wearing face masks of high efficiencies. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a novel coronavirus, causes coronavirus disease 2019 (COVID-19). Otologic surgeries with drilling by powered instruments induce significant aerosols, which may induce SARS-CoV-2 transmission to medical staff if SARS-CoV-2 exists in the middle ear and mastoid cavity. During a COVID-19 pandemic, therefore, confirming a negative COVID-19 test prior to otologic surgery is recommended. However, previous coronavirus studies demonstrated that coronavirus was detected in the middle ear in some patients even though the polymerase chain reaction (PCR) test using their nasopharyngeal swab was negative. This study aimed to elucidate the probability of a positive SARS-CoV-2 PCR test in the middle ear or mastoid specimens from otologic surgery patients in whom SARS-CoV-2 was not detected by preoperative PCR test using a nasopharyngeal swab. We conducted a prospective, multicenter clinical study. Between April 2020 and December 2021, during the COVID-19 pandemic, 251 ears of the 228 participants who underwent otologic surgery were included in this study. All participants had no symptoms suggesting COVID-19 or close contact with a confirmed COVID-19 patient two weeks prior to the surgery. They were also negative in the SARS-CoV-2 PCR tests using a nasopharyngeal swab before surgery. We collected mucosa, granulation, bone dust with mucosa or fluid from the middle ear or mastoid for the SARS-CoV-2 PCR tests during each otologic surgery. The median age of the participants at surgery was 31.5 years old. Mastoidectomy using a powered instrument was conducted in 180 of 251 otologic surgeries (71.8%). According to intraoperative findings, active inflammation in the middle ear or mastoid cavities was evident in 20 otologic surgeries (8.0%), while minor inflammation was observed in 77 (30.7%). All SARS-CoV-2 PCR tests of otologic specimens showed a negative result. No patient suffered from COVID-19 within two months after otologic surgery. Furthermore, no hospital-acquired infections associated with otologic surgery occurred in our institutions Our results showed that PCR testing did not detect SARS-CoV-2 in middle ear and mastoid specimens, suggesting that the risk of transmission of SARS-CoV-2 is not high in otologic surgeries even using powered instruments when both clinical and laboratory tests are confirmed to be negative for COVID-19. [ABSTRACT FROM AUTHOR]

IntroductionThe COVID-19 pandemic continues to ravage the world, and mutations of the SARS-CoV-2 continues. The new strain has become more transmissible. The role of aerosol transmission in the pandemic deserves great attention.MethodsIn this observational study, we collected data from market customers and stallholders who had been exposed to the virus in the Qingkou night market on July 31 and were subsequently infected. We analyzed the possible infection zones of secondary cases and aerosol suspension time in ambient air. We described and analyzed the characteristics of the secondary cases and the transmission routes for customers.ResultsThe point source outbreak of COVID-19 in Qingkou night market contained a cluster of 131 secondary cases. In a less-enclosed place like the Qingkou night market, aerosols with BA.5.2 strain released by patients could suspend in ambient air up to 1 h 39 min and still be contagious.ConclusionAerosols with viruses can spread over a relatively long distance and stay in ambient air for a long time in a less enclosed space, but shorter than that under experimental conditions. Therefore, the aerosol suspension time must be considered when identifying and tracing close contact in outbreak investigations.

The importance of effective ventilation as one of the measures against COVID-19 is widely recognized worldwide. In Japan, at the early stage of the pandemic, in March 2020, an official announcement was made about basic ventilation measures against COVID-19. WHO also used the term "long-range aerosol or long-range airborne transmission" for the first time in December 2021. Based on the aerosol infection control measures before 2021 by the Japanese government, we conducted experiments on methods related to partition placement as an element of effective ventilation methods. In July 2022, the governmental subcommittee on Novel Coronavirus Disease Control provided an emergent proposal about effective ventilation methods to prevent two types of aerosol infection; infection by large aerosol on the air current and infection by small floating aerosol diffusion in a room. They also showed the way of setting droplet prevention partitions, which do not block off ventilation based on this investigation's results. [ABSTRACT FROM AUTHOR]

Although it is well established that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be transmitted through aerosols, the mode of long-range aerosol transmission in high-rise buildings remains unclear. In this study, we analyzed an outbreak of coronavirus disease 2019 (COVID-19) that occurred in a high-rise building in China. Our objective was to investigate the plausibility of aerosol transmission of SARS-CoV-2 by testing relevant environmental variables and measuring the dispersion of a tracer gas in the drainage system of the building. The outbreak involved 7 infected families, of which 6 were from vertically aligned flats on different floors. Environmental data revealed that 3 families' bathrooms were contaminated by SARS-CoV-2. In our tracer experiment, we injected tracer gas (CO2) into the dry floor drains and into water-filled toilets in the index case' s bathroom. Our findings showed that the gas could travel through vertical pipes by the dry floor drains, but not through the water of the toilets. This indicates that dry floor drains might facilitate the transmission of viral aerosols through the sewage system. On the basis of circumstantial evidence, long-range aerosol transmission may have contributed to the community outbreak of COVID-19 in this high-rise building. The vertical transmission of diseases through aerosols in high-rise buildings demands urgent attention. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 is inactivated in aerosol (its primary mode of transmission) by means of radiated microwaves at frequencies that have been experimentally determined. Such frequencies are best predicted by the mathematical model suggested by Taylor, Margueritat and Saviot. The alignment between such mathematical prediction and the outcomes of our experiments serves to reinforce the efficacy of the radiated microwave technology and its promise in mitigating the transmission of SARS-CoV-2 in its naturally airborne state.

Aerosol transmission has been officially recognized by the world health authority resulting from its overwhelming experimental and epidemiological evidences. Despite substantial progress, few additional actions were taken to prevent aerosol transmission, and many key scientific questions still await urgent investigations. The grand challenge, the effective control of aerosol transmission of COVID-19, remains unsolved. A better understanding of the viral shedding into the air has been developed, but its temporal pattern is largely unknown. Sampling tools, as one of the critical elements for studying SARS-CoV-2 aerosol, are not readily available around the world. Many of them are less capable of preserving the viability of SARS-CoV-2, thus offering no clues about viral aerosol infectivity. As evidenced, the viability of SARS-CoV-2 is also directly impacted by temperature, humidity, sunlight, and air pollutants. For SARS-CoV-2 aerosol detection, liquid samplers, together with real-time polymerase chain reaction (RT-PCR), are currently used in certain enclosed or semi-enclosed environments. Sensitive and rapid COVID-19 screening technologies are in great need. Among others, the breath-borne-based method emerges with global attention due to its advantages in sample collection and early disease detection. To collectively confront these challenges, scientists from different fields around the world need to fight together for the welfare of mankind. This review summarized the current understanding of the aerosol transmission of SARS-CoV-2 and identified the key knowledge gaps with a to-do list. This review also serves as a call for efforts to develop technologies to better protect the people in a forthcoming reopening world.

The legendary Greek philosopher, Aristotle once said that “Man is by nature a social animal.” Biological transmission of any disease is linked to the social contact of human beings. Respiratory infections are the best example of it. Pandemics of respiratory viral illnesses in history have taught a lesson of simple measures to protect ourselves by using face masks. Since the last nine centuries, scientists have struggled to come up with the masks giving 95%–99% of protection against respiratory pathogens. Through this article, we aim to review the evolution of the mask through times, with the objective of finding its effectiveness in preventing infections and also its role as a source of infection. Various online databases were searched to find articles that provided description of evolution of the mask.

Current research on airborne transmission of African swine fever virus (ASFV), porcine epidemic diarrhoea virus (PEDV), avian influenza (AIV), porcine reproductive and respiratory syndrome virus (PRRSV), and foot and mouth disease virus (FMDV) was reviewed to evaluate commonalities, knowledge gaps, and methodologies of studying airborne transmission of animal diseases. The reviewed studies were categorised as short-range transmission (within a single facility) and long-range transmission (beyond a single site). Short-range airborne transmission was demonstrated for at least one strain of the above-mentioned pathogens in experimental settings. Most studies reported in the literature concern FMDV, with limited information for ASFV and PEDV, particularly for short-range airborne transmission. Air sampling upwind, downwind, and within infected facilities has been commonly used to demonstrate long-range airborne transmission. The amount of evidence from air sampling for each of the reviewed viruses varies from no evidence on ASFV to evidence from multiple settings for AIV. Computer modelling has been used to study past outbreaks of infectious diseases to assess the contribution of airborne transmission with a multitude of computer models reported in the literature for simulating long-range airborne transmission of FMDV based on past outbreaks. This has resulted in predictive tools for assessing future risk of airborne transmission. Some important computer models are based on epidemiology analysis, weather analysis, and air dispersion. Few models are reported for ASFV, PEDV, and PRRSV. Studies in the literature indicate that airborne transmission is generally affected by virus strain, aerosol type, shedding duration and concentration, environmental conditions, and infectious dose. [Display omitted] • A literature review of airborne transmission of five viral animal diseases. • Short-distance airborne transmission confirmed for at least 1 strain of each virus. • Possibility of long-distance airborne transmission demonstrated by air sampling. • Factors like aerosol type, strain, and infectious dose affect airborne transmission. • Computer modelling of airborne transmission potentially provides a prediction tool. [ABSTRACT FROM AUTHOR]

Currently, it is believed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an airborne virus, and virus-containing aerosol particles have been found concurrent with the onset of COVID-19, which may contribute to the noncontact transmission of SARS-CoV-2. Exploring agents to block SARS-CoV-2 transmission is of great importance to prevent the COVID-19 pandemic. In this study, we found that inactivated Parapoxvirus ovis (iORFV), a kind of immunomodulator, could compress the proportion of small particle aerosols exhaled by Syrian golden hamsters. Notably, the concentration of SARS-CoV-2 RNA-containing aerosol particles was significantly reduced by iORFV in the early stages after viral inoculation. Importantly, smaller aerosol particles (<4.7pm) that carry infectious viruses were completely cleared by iORFV. Consistently, iORFV treatment completely blocked viral noncontact (aerosol) transmission. In summary, iORFV may become a repurposed agent for the prevention and control of COVID-19 by affecting viral aerosol exhalation and subsequent viral transmission. [ABSTRACT FROM AUTHOR]

COVID‐19 has highlighted the need for indoor risk‐reduction strategies. Our aim is to provide information about the virus dispersion and attempts to reduce the infection risk. Indoor transmission was studied simulating a dining situation in a restaurant. Aerosolized Phi6 viruses were detected with several methods. The aerosol dispersion was modeled by using the Large‐Eddy Simulation (LES) technique. Three risk‐reduction strategies were studied: (1) augmenting ventilation with air purifiers, (2) spatial partitioning with dividers, and (3) combination of 1 and 2. In all simulations infectious viruses were detected throughout the space proving the existence long‐distance aerosol transmission indoors. Experimental cumulative virus numbers and LES dispersion results were qualitatively similar. The LES results were further utilized to derive the evolution of infection probability. Air purifiers augmenting the effective ventilation rate by 65% reduced the spatially averaged infection probability by 30%–32%. This relative reduction manifests with approximately 15 min lag as aerosol dispersion only gradually reaches the purifier units. Both viral findings and LES results confirm that spatial partitioning has a negligible effect on the mean infection‐probability indoors, but may affect the local levels adversely. Exploitation of high‐resolution LES jointly with microbiological measurements enables an informative interpretation of the experimental results and facilitates a more complete risk assessment. [ABSTRACT FROM AUTHOR]

Hospital‐acquired infections (HAIs) are a global challenge incurring mortalities and high treatment costs. The environment plays an important role in transmission due to contaminated air and surfaces. This includes microorganisms' deposition from the air onto surfaces. Quantifying the deposition rate of microorganisms enables understanding surface contamination and can inform strategies to mitigate the infection risk. We developed and validated a novel Automated Multiplate Passive Air Sampling (AMPAS) device. This enables sequences of passive deposition samples to be collected over a controlled time period without human intervention. AMPAS was used with air sampling to measure the effect of ventilation rate and spatial location on the deposition rate of aerosolized Staphylococcus aureus in a 32 m3 chamber. Increasing the ventilation rate from 3 to 6 ACH results in a reduction of microbial load in the air and on surfaces by 45% ± 10% and 44% ± 32%, respectively. The deposition rate onto internal surfaces λd was calculated as 1.38 ± 0.48 h−1. Samples of airborne and surface microorganisms taken closer to the ventilation supply showed a lower concentration than close to the extract. The findings support the importance of controlling the ventilation and the environmental parameters to mitigate both air and surface infection risks in the hospital environment. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 2019 (COVID-19) remain a major global health challenge, with aerosol transmission being the primary route of spread. The use of antivirals as medical countermeasures to control SARS-CoV-2 transmission and spread is promising but remains to be clarified. The current study established and used an in vivo hamster aerosol transmission model system to evaluate the efficacy of the protease inhibitor ensitrelvir to prevent the spread of SARS-CoV-2. Male Index Syrian hamsters were intranasally infected with SARS-CoV-2, paired with naïve Contact hamsters, and co-housed for 12 h under conditions to allow for only aerosol transmission. The Index hamsters were treated three times with ensitrelvir starting 8 h post infection, or the Contact hamsters were treated once with ensitrelvir 12 h prior to co-housing. Viral infection and transmission were monitored by evaluating nasal lavage fluid, lung tissues, and body and lung weights. Post-infection administration of ensitrelvir to Index hamsters suppressed virus shedding in a dose-dependent manner. Pre-exposure administration of 750 mg/kg ensitrelvir to naïve Contact hamsters also protected against aerosol SARS-CoV-2 infection in a dose-dependent manner. Furthermore, pre-exposure treatment of 750 mg/kg ensitrelvir supressed body weight loss and lung weight increase of aerosol infected hamsters compared to vehicle-treated hamsters. These findings suggest that ensitrelvir may prevent SARS-CoV-2 spread when administered to infected patients and may prevent or limit SARS-CoV-2 infection when prophylactically administered to non-infected individuals. Both approaches may help protect at-risk individuals, such as family members living with SARS-CoV-2-infected patients., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The authors declare the following competing financial interest(s): (1) Shionogi & Co., Ltd. has applied for a patent on ensitrelvir(2) Masaaki Nakashima, Haruaki Nobori, Takayuki Kuroda, Alice Shimba, Satoshi Miyagawa, Akane Hayashi, Kazumi Matsumoto, Mei Yoshida, Kaoru Baba, Teruhisa Kato, and Keita Fukao are employees of Shionogi & Co., Ltd. and its subsidiary company, Shionogi TechnoAdvance Research Co., Ltd.(3) Some of the authors are shareholders in Shionogi & Co., Ltd., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The legendary Greek philosopher, Aristotle once said that "Man is by nature a social animal." Biological transmission of any disease is linked to the social contact of human beings. Respiratory infections are the best example of it. Pandemics of respiratory viral illnesses in history have taught a lesson of simple measures to protect ourselves by using face masks. Since the last nine centuries, scientists have struggled to come up with the masks giving 95%-99% of protection against respiratory pathogens. Through this article, we aim to review the evolution of the mask through times, with the objective of finding its effectiveness in preventing infections and also its role as a source of infection. Various online databases were searched to find articles that provided description of evolution of the mask. [ABSTRACT FROM AUTHOR]

We investigated the risk of coronavirus disease (COVID-19)­ patients transmitting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to emergency medical service (EMS) providers, stratified by aerosol-generating procedures (AGP), in King County, Washington, USA, during February 16–July 31, 2020. We conducted a retrospective cohort investigation using a statewide COVID-19 registry and identified 1,115 encounters, 182 with ≥1 AGP. Overall, COVID-19 incidence among EMS personnel was 0.57 infections/10,000 person-days. Incidence per 10,000 person-days did not differ whether or not infection was attributed to a COVID-19 patient encounter (0.28 vs. 0.59; p>0.05). The 1 case attributed to a COVID-19 patient encounter occurred within an at-risk period and involved an AGP. We observed a very low risk for COVID-19 infection attributable to patient encounters among EMS first responders, supporting clinical strategies that maintain established practices for treating patients in emergency conditions.

The risk of COVID-19 infection from virulent aerosols is particularly high indoors. This is especially true for classrooms, which often do not have pre-installed ventilation and are occupied by a large number of students at the same time. It has been found that precautionary measures, such as the use of air purifiers (AP), physical distancing, and the wearing of masks, can reduce the risk of infection. To quantify the actual effect of precautions, it is not possible in experimental studies to expose subjects to virulent aerosols. Therefore, in this study, we develop a computational fluid dynamics (CFD) model to evaluate the impact of applying the aforementioned precautions in classrooms on reducing aerosol concentration and potential exposure in the presence of index or infected patients. A CFD-coupled Wells–Riley model is used to quantify the infection probability (IP) in the presence of index patients. Different cases are simulated by varying the occupancy of the room (half/full), the volumetric flow rate of the AP, two different locations of the AP, and the effect of wearing masks. The results suggest that using an AP reduces the spread of virulent aerosols and thereby reduces the risk of infection. However, the risk of the person sitting adjacent to the index patient is only marginally reduced and can be avoided with the half capacity of the class (physical distancing method) or by wearing face masks of high efficiencies.

Background Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) superspreading events suggest that aerosols play an important role in driving the coronavirus disease 2019 (COVID-19) pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5 μm) and fine (≤5 μm) respiratory aerosols produced when breathing, talking, and singing. Methods Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. Results Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. Conclusions Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging; whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies. [ABSTRACT FROM AUTHOR]

Background: Recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission through exposure to aerosols has been suggested. Therefore, we investigated the possibility of aerosol SARS-CoV-2 transmission within an apartment complex where residents reported testing positive for SARS-CoV-2 despite having no direct contact with other SARS-CoV-2-infected people.Methods: Information on symptom onset and exposure history of the patients was collected by global positioning system (GPS) tracking to investigate possible points of contact or spread. Samples collected from patients and from various areas of the complex were analyzed using RNA sequencing. Phylogenetic analysis was also performed.Results: Of 19 people with confirmed SARS-CoV-2 infection, 5 reported no direct contact with other residents and were from apartments in the same vertical line. Eight environmental samples tested positive for the virus. Phylogenetic analyses revealed that 3 of the positive cases and 1 environmental sample belonged to the B.1.497 lineage. Additionally, 3 clinical specimens and 1 environmental sample from each floor of the complex had the same amino acid substitution in the ORF1ab region.Conclusions: SARS-CoV-2 transmission possibly occurs between different floors of an apartment building through aerosol transmission via nonfunctioning drain traps. [ABSTRACT FROM AUTHOR]