Aerosolized Transmission

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Re: Aerosolized Transmission

Post by trader32176 »

Cloth face masks can be as effective as surgical masks in reducing transmission of COVID-19

4/28/21 ... ID-19.aspx

Researchers from the Universities of Bristol and Surrey have found that well-fitting, three-layered cloth masks can be as effective at reducing the transmission of COVID-19 as surgical masks.

At the height of the COVID-19 pandemic, 139 countries mandated the use of face coverings in public space such as supermarkets and public transports. The World Health Organization also advises the use of face coverings and offers guidance on their effective features. Face coverings suppress the onward transmission of COVID-19 through exhalation and protect the wearer on inhalation.

In a paper published by the Physics of Fluids journal, the researchers detail how they looked at how liquid droplets are captured and filtered out in cloth masks by reviewing and modelling filtration processes, including inertial impaction.

Inertial impaction does not filter as a sieve or colander does - it works by forcing the air in your breath to twist and turn inside the mask so much that the droplets can't follow the path of the air. Instead, the droplets crash into fibres inside the mask to prevent inhalation.

The team found that, under ideal conditions and dependent on the fit, three-layered cloth masks can perform similarly to surgical masks for filtering droplets - with both reducing exposure by around 50 to 75 per cent. For example, if an infected person and a healthy individual are both wearing masks, scientists believe this could result in up to 94 per cent less exposure.

" While wearing a simple and relatively inexpensive cloth face mask cannot eliminate the risk of contracting COVID-19, measurements and our theoretical model suggests they are highly effective in reducing transmission. We hope that our work inspires mask designs to be optimised in the future and we hope it helps to remind people of the importance of continuing to wear masks while COVID-19 remains present in the community."

- Dr Richard Sear, Study Co-Author and Leader of the Soft Matter Group, University of Surrey


University of Surrey

Journal reference:

Robinson, J.F., et al. (2021) Efficacy of face coverings in reducing transmission of COVID-19: Calculations based on models of droplet capture. Physics of Fluids.
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Re: Aerosolized Transmission

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HEPA filters reduce respiratory aerosols produced during intense exercise

5/5/21 ... rcise.aspx

A pair of Mayo Clinic studies shed light on something that is typically difficult to see with the eye: respiratory aerosols. Such aerosol particles of varying sizes are a common component of breath, and they are a typical mode of transmission for respiratory viruses like COVID-19 to spread to other people and surfaces.

Researchers who conduct exercise stress tests for heart patients at Mayo Clinic found that exercising at increasing levels of exertion increased the aerosol concentration in the surrounding room. Then also found that a high-efficiency particulate air (HEPA) device effectively filtered out the aerosols and decreased the time needed to clear the air between patients.

" Our work was conducted with the support of Mayo Cardiovascular Medicine leadership who recognized right at the start of the pandemic that special measures would be required to protect patients and staff from COVID-19 while continuing to provide quality cardiovascular care to all who needed it. Since there was no reliable guidance on how to do this, we put a research team together to find answers through scientific testing and data. We are happy to now share our findings with everyone around the world."

- Thomas Allison, PhD, Director of Cardiopulmonary Exercise Testing, Mayo Clinic

Dr. Allison is senior author of both studies.

To characterize the aerosols generated during various intensities of exercise in the first study, Dr. Allison's team set up a special aerosol laboratory in a plastic tent with controlled airflow. Two types of laser beam particle counters were used to measure aerosol concentration at the front, back and sides of a person riding an exercise bike. Eight exercise volunteers wore equipment to measure their oxygen consumption, ventilation and heart rate.

During testing, a volunteer first had five minutes of resting breathing, followed by four bouts of three-minute exercise staged ? with monitoring and coaching ? to work at 25%, 50%, 75% and 100% of their age-predicted heart rate. This effort was followed by three minutes of cooldown. The findings are publicized online in CHEST.

The aerosol concentrations increased exponentially throughout the test. Specifically, exercise at or above 50% of resting heart rate showed significant increases in aerosol concentration.

"In a real sense, I think we have proven dramatically what many suspected ? that is why gyms were shut down and most exercise testing laboratories closed their practices. Exercise testing was not listed as an aerosol-generating procedure prior to our studies because no one had specifically studied it before. Exercise generates millions of respiratory aerosols during a test, many of a size reported to have virus-carrying potential. The higher the exercise intensity, the more aerosols are produced," says Dr. Allison.

The follow-up study led by Dr. Allison focused on how to mitigate the aerosols generated during exercise testing by filtering them out of the air immediately after they came out of the subject's mouth. Researchers used a similar setup with the controlled airflow exercise tent, particle counter and stationary bike, but added a portable HEPA filter with a flume hood.

Six healthy volunteers completed the same 20-minute exercise test as the previous study, first without the mitigation and then with the portable HEPA filter running.

Also, a separate experiment tested aerosol clearance time in the clinical exercise testing laboratories by using artificially generated aerosols to test how long it took for 99.9% of aerosols to be removed. Researchers performed the test first with only existing heating, ventilation and air conditioning, and then with the addition of the portable HEPA filter running.

"Studying clearance time informed us of how soon we could safely bring a new patient into the laboratory after finishing the test on the previous patient. HEPA filters cut this time by 50%, allowing the higher volume of testing necessary to meet the clinical demands of our Cardiovascular Medicine practice," says Dr. Allison.

"We translated CDC (Centers for Disease Control and Prevention) guidelines for aerosol mitigation with enhanced airflow through HEPA filters and showed that it worked amazingly well for exercise testing. We found that 96% plus or minus 2% of aerosols of all sizes generated during heavy exercise were removed from the air by the HEPA filter. As a result, we have been able to return to our practice of performing up to 100 stress tests per day without any recorded transmission of COVID in our exercise testing laboratories," says Dr. Allison.


Mayo Clinic

Journal reference:

Sajgalik, P., et al. (2021) Characterization of Aerosol Generation during Various Intensities of Exercise. CHEST.
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Re: Aerosolized Transmission

Post by trader32176 »

Long and short-range risk of airborne transmission of SARS-CoV-2

5/12/21 ... CoV-2.aspx

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has contributed to significant morbidity, mortality, and economic losses. To date, the virus has infected over 159 million individuals and caused over 3.3 million deaths the world over. The need to mitigate this pandemic has the scientific community revisiting the transmissibility, mechanism, and risk of transmission under certain conditions.

In a recent research study, Florian Poydenot et al. performed a quantitative assessment of indoor and outdoor transmission risk; and how to reduce the contributions of public spaces to the propagation of SARS-CoV-2. The study is published on the medRxiv*, a preprint server for health sciences.

“A quantitative analysis of the viral transmission risk in public spaces allows us to identify the dominant mechanisms that a proactive public health policy can act upon to reduce risk, and to evaluate the reduction of risk that can be obtained.”

The researchers showed that long-range aerosol transmission is controlled by the flow rate of fresh air and by the mask filtering quality, and is quantitatively related to the CO2 concentration, regardless of the room volume and the number of people. Importantly, they found that it is quantitatively related to the CO2 concentration, regardless of the room volume and the number of people.

Using dedicated dispersion experiments performed in two shopping malls, the researchers experimentally investigated the short-range airborne transmission. They found that the exhaled aerosols are dispersed by turbulent draughts in the shape of a cone, leading to a concentration inversely proportional to the squared distance and the flow velocity.

They elaborated on various techniques available to reduce the viral transmission risk in public places. In this study, the researchers showed that the average infection dose, called the viral quantum, can be determined from the epidemiological data (in a manner consistent with experimental biological data).

In the study, the researchers defined and modeled the transmission risk, focusing on the long-range airborne transmission risk (measured using carbon dioxide concentration) and on the short-range airborne transmission risk indoor and outdoor. They examined the quanta generation rate and the dose-response function.

They also looked at the respiratory mask efficiency based on the droplet size distribution, evaporation of liquid droplets (controlled by the ambient relative humidity RH), and the enrichment issue.

It is established that the SARS-CoV-2 is easily spread during expiratory human activities (including breathing, speaking, singing, or laughing), which may cause asymptomatic and pre-symptomatic transmission (as aerosols). Also, indoor transmission is observed to be 19 times more prevalent than outdoors.

Measuring the viral transmission risk in public places (such as schools, offices, university lecture halls, museums, theatres, or shopping centers) and outdoors is a problem. The researchers in this study characterized the dominant transmission routes in social activities and tried to identify efficient ways of reducing the risk of epidemic contamination in public spaces.

In this comprehensive study, the researchers define the risk of transmission in a public space and document its dependence on the number of people present, the average time they are present, the available volume in which aerosols are stored, and the level of ventilation.

They determined the risk assessment for long-range airborne transmission and quantitatively related it to the CO2 concentration.

Interestingly the study showed that short-range airborne transmission, localized in the wake of people infected by SARS-CoV-2, obeys the same physical laws indoors and outdoors.

In the experimental measurements of turbulent dispersion of the passive tracer (CO2) performed in the shopping centers, they found that the turbulent diffusion is due to a small permanent airflow leading to a rapid spatial decay of the tracer concentration. They report that the additional risk when staying in the wake from other people is determined quantitatively as a function of the distance downwind.

In conclusion, the researchers provide a practical definition of the risk r (defined as the average secondary infections per initially infected person) associated with public space. It is related to the integrated quantum emission, to the mask filtration factor (λ), and to the CO2 concentration, which quantifies the dilution factor between exhaled and inhaled air.

Based on this risk assessment, the researchers defined quantitative standards (occupation capacity, CO2 level, ventilation, masks) to be implemented in public spaces to reach the acceptable residual risk.

The goal in the efforts to mitigate COVID-19 is to reduce the pandemic to a level where the overall reproduction rate of the virus is below one. This study provides valuable quantitative guidance for making rational public health policy decisions to prevent the dominant routes of viral transmission through reinforced ventilation, air purification, mechanical dispersion using fans, and incentivizing the wearing of correctly fitted, quality facial masks (surgical masks, possibly covered by another fabric mask, or non-medical FFP2 masks).

These measures taken together significantly reduce the airborne transmission risk of SARS-CoV-2.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Risk assessment for long and short-range airborne transmission of SARS-CoV-2, indoors and outdoors, using carbon dioxide measurements, Florian Poydenot, Ismael Abdourahamane, Elsa Caplain, Samuel Der, Jacques Haiech, Antoine Jallon, Inés Khoutami, Amir Loucif, Emil Marinov, Bruno Andreotti, medRxiv 2021.05.04.21256352; doi:, ... 21256352v1
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Re: Aerosolized Transmission

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Non-droplet routes of SARS-CoV-2 transmission

5/26/21 ... ssion.aspx

In a recent review article published in the Science of The Total Environment journal, a group of Polish researchers discussed the different transmission routes of the severe acute respiratory coronavirus 2 (SARS-CoV-2), the virus responsible for the coronavirus disease 2019 (COVID-19). In their work, the researchers focused on the extent of SARS-CoV-2 survival in the environment, particularly in sewages and contaminated surfaces.


As of May 26, 2021, SARS-CoV-2 has infected over 167 million individuals, which has led to almost 3.5 million deaths worldwide. It is generally thought that the incubation period of SARS-CoV-2 lasts from 2 to 12 days, with an average of 5.1 days.

Because of its high transmissibility, which primarily occurs in aerosols, public health officials and medical professionals worldwide are highly interested in better understanding all possible modes of SARS-CoV-2 transmission. Expanding the knowledge on the survivability of the virus on various surfaces and discharges and identifying effective disinfection procedures remain crucial to adequately reducing the transmission of this coronavirus.

The Science of The Total Environment review article summarizes the current knowledge on SARS-CoV-2 transmission and survival, particularly via non-droplet routes. The authors of this paper emphasized the need for a thorough investigation of the COVID-19 patient's environment.

"This article aimed to review the available data on the non-droplet routes of the spread of SARS-CoV-2 and related coronaviruses (including SARS-CoV-1, MERS) such as wastewater, soil, and surface, and methods of their elimination."

A review of SARS-CoV-2 transmission sources

In their review, the authors used relevant keywords and performed a manual search of electronic databases such as Pubmed, Google Scholar, Web of Science, and the medRxiv preprint server for primary articles and abstracts that were published between July 1, 2020, and October 17, 2020. They selected 128 peer-reviewed articles, review articles, and other relevant documents published in 2020, as well as 60 relevant articles published before 2020.

SARS-CoV-2 in aerosols

After reviewing these published pieces, the authors discussed the presence of SARS-CoV-2 in the air and on surfaces, as well as documented cases of SARS-CoV-2 detected in water, sewage, and soil.

When COVID-19 patients speak, cough, or sneeze, they disperse aerosols containing infectious viral particles to their surrounding environment. Overall, the spread of these droplets is considered to be the main transmission route for SARS-CoV-2.

When present in an aerosol, the half-life of SARS-Cov-2 is about 3 hours. This half-life represents the amount of time required for half of the viral genetic material to die. Although SARS-CoV-2 can persist in the environment for clearly extensive periods, in particular closed environments like a hospital, the authors found that stringent disinfection procedures successfully eliminate the genetic material of SARS-CoV-2 in these closed environments.

SARS-CoV-2 on various surfaces

In addition to aerosols, several other modes of viral transmission may add to a rapid increase in infection rates over a short period of time. Various surfaces touched by infected persons, as well as the contamination of water, sewage, garbage, or soil, are all likely routes of SARS-CoV-2 transmission.

The duration of SARS-CoV-2 on different surfaces varies significantly, depending on the surface. A latex glove that has been contaminated with SARS-CoV-2, for example, will have viable viral genetic material remaining on its surface for a maximum of 8 hours. This is comparable to the duration of SARS-CoV-2 on wood, metal, and paper surfaces, which is between 4 and 5 days.

In addition to these surfaces, SARS-CoV-2 also remains on everyday items such as mobile phones, desktop computers, keyboards, printers, remote controls for televisions, elevator buttons, and much more. The authors also found that the persistence of SARS-CoV-2 in the hospital environment, particularly areas that are often touched by both patients and healthcare professionals, is a significant problem.

SARS-CoV-2 in water, sewage, and soil

The RNA of SARS-CoV-2, as well as several live viruses, have been detected in stool and urine samples of infected individuals, thus indicating their potential as open transmission routes.

"It is particularly relevant in areas where people have contact with feces or sewage containing virus particles, i.e., contaminated water reservoirs with raw discharges," noted the authors.

A recent study showed that the lowest observed percentage of SARS-CoV-2 positive samples was for toilets (8.70%), followed by shower traps (18.75%) and sink traps (19.23%).

"Guaranteeing drinking water safety, sewage collection, and maintaining effective hygiene during the COVID-19 pandemic, play a key role in ensuring public health safety."

While there is no data for developing countries, the genetic material of SARS-CoV-2 was not present in wastewater rivers that were tested in Japan. Contrastingly, SARS-CoV-2 RNA was found in river samples obtained from Quito, Ecuador.

In a 2003 report on SARS-CoV-1 in Hong Kong, the virus was found to spread among residents from a sewer pipe leakage in an apartment, which contributed to the aerosolization of water droplets containing virus particles. "It can be assumed that a similar situation can apply to SARS-CoV-2," observed the authors of the current study.

Taken together, the presence of SARS-CoV-2 in untreated sewage or waters is suggestive of possible soil penetration with its particles.

"Soil, a matrix rich in organic substances that can protect various viruses, can probably act as a reservoir for SARS-CoV-2, being a secondary element in aerosol-mediated dispersion."

Appropriate disinfection methods

To control and contain the transmission of SARS-CoV-2, it is imperative to implement effective decontamination methods for these environments. The effective elimination of SARS-CoV-2 from surfaces can be achieved through the use of 65–70% ethanol, 0.5% hydrogen peroxide, or 0.1% sodium hypochlorite.

Within the air, frequent ventilation with 6 to 12 changes per hour is recommended. Additionally, certain air purification technologies, such as that which is offered by ActivePure Technologies LLC, have been found to inactive airborne SARS-CoV-2 by up to 99.9%.

Despite its persistence in wastewaters, several disinfection methods have the potential to mitigate the risk of spreading SARS-CoV-2. These include chemical disinfection through the use of chlorine solutions like sodium hypochlorite and chlorine dioxide and physical disinfection via ultraviolet (UV) and gamma radiation and thermal inactivation. Notably, mechanical disinfection methods, such as micro-and ultrafiltration, cannot mitigate the spread of any viruses, including SARS-CoV-2.

This review collates the information that is currently available on how SARS-CoV-2 is spread. Moreover, this article raises important questions on the non-droplet spreading routes within the environment that require public attention in the global fight against this pandemic.

Journal reference:

Wiktorczyk-Kapischke, N., Grudlewska-Buda, K., Wałecka-Zacharska, E., et al. (2021). SARS-CoV-2 in the environment—Non-droplet spreading routes. Science of The Total Environment 770. doi:10.1016/j.scitotenv.2021.145260.
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Re: Aerosolized Transmission

Post by trader32176 »

Rearranging orchestral musicians to reduce disease-spreading aerosols

6/24/21 ... osols.html

A team of researchers at the University of Utah Salt Lake City has found, via simulation, that it is possible to rearrange musicians playing wind instruments in an orchestra to reduce the spread of disease-laden aerosols. In their paper published in the journal Science Advances, the group describes simulations they ran that showed airflow patterns during orchestral performances and what they found.

As the pandemic spread across the world, one of the groups immediately impacted was musicians, particularly those who play wind instruments. Once it was determined that the virus behind COVID-19 was carried through the air as part of aerosols, officials began canceling orchestral performances.

The pandemic also prevented musicians from practicing together, which is essential for maintaining skills. Now, even as lockdowns are eased in many countries, orchestral performances have still not resumed due to fears of spreading the diseases among musicians who have not been vaccinated. In this new effort, the researchers have found a way to minimize the risk involved in orchestral rehearsals and performances by rearranging where the players sit as they play.

To learn more about the flow of air and the aerosols in it during orchestral performances, the researchers gathered data from prior experiments showing how air moves after being expelled from different instruments. This data was put into an air movement simulation, along with other parameters, such as ventilation for the given venue.

The team then began tinkering with the seating arrangements and discovered that by making certain changes they could reduce the viral load in the air where the musicians were playing. They found, for example, that putting percussionists closer to the center of the group and those playing wind instruments around the fringes—and as close as possible to air vents—they could dramatically reduce the spread of aerosols.

The researchers next moved their experiment to the real world by having vaccinated players for the Utah Symphony change their seating arrangements to match the simulations. The researchers then tested the air as the musicians played. In studying the data, they found that the new seating arrangement reduced concentrations of virtual viral loads by a factor of 100—from 0.01 to just 0.001 particles per liter of air.

More information: Hayden A. Hedworth et al, Mitigation strategies for airborne disease transmission in orchestras using computational fluid dynamics, Science Advances (2021). DOI: 10.1126/sciadv.abg4511
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Re: Aerosolized Transmission

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Study reports low risk for COVID-19 in Emergency Medical Service personnel exposed to aerosol-generating procedures

7/13/21 ... dures.aspx

Amid the coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), healthcare providers working on the frontlines are a particularly high-risk group for infection. Though vaccination efforts prioritized this group, working directly with COVID-19 patients makes them at risk of contracting the virus.

The U.S. Centers for Disease Control and Prevention (CDC) reports that emergency medical service personnel exposed to aerosol-generating procedures (AGP) on COVID-19 patients are generally at low risk of infection. The findings, published in CDC’s Emerging Infectious Diseases, support clinical strategies that maintain established and evidence-based practices for emergency conditions.

In the study, the researchers investigated the risk of COVID-19 patients transmitting SARS-CoV-2 to emergency medical service (EMS) providers providing aerosol-generating procedures (AGP) in King County, Washington, in the United States.

COVID-19 and aerosol-generating procedures (AGP)

Respiratory exposure is the primary mode of COVID-19 transmission. When an infected patient coughs, sneezes, breathes or speaks, virus-laden droplets are expelled into the air. Inhaling infectious droplets or touching contaminated surfaces (known as ‘fomites’) could lead to infection.

The global pandemic has also forced EMS providers to consider how best to manage their potential exposure since they cater to all patients with unknown infections status. In previous coronavirus outbreaks, like the severe acute respiratory syndrome (SARS) in 2003 and the Middle East respiratory syndrome (MERS) in 2012, many healthcare workers became infected while caring for patients.

Though many studies have tackled the risk of patients transmitting SARS-CoV-2 to healthcare workers, little is known about transmitting it to first-line responders or emergency medical responders.

Guidelines have improved over the years to reduce the risk of transmission, especially through aerosolizing procedures used for airway management and cardiopulmonary resuscitation (CPR). Having a better understanding of the risks tied to patient care can help improve clinical practices, infection control measures, and the use of personal protective equipment (PPE) strategies.

The study

The researchers performed a retrospective cohort study to evaluate the risk for SARS-CoV-2 infection among EMS providers caring for patients between February 16 and July 31, 2020, in King County, Washington. The study considered all EMS provider-patient encounters and individual EMS providers involved.

The team utilized a statewide COVID-19 registry to arrive at the study findings and identified 1,115 encounters, 182 with more than one AGPs, including endotracheal intubation, supraglottic airway insertion, bag-valve-mask (BVM) ventilation, nebulizer medication therapy, and continuous positive airway pressure nonrebreather mask oxygen.

Further, the study considered EMS providers at risk for transmission from a patient for two to 14 days after an encounter with a COVID-19 patient. If an EMS provider tested positive for SARS-CoV-2 in the two to 14 days incubation period after exposure, the infection was tied to the encounter.

The results showed that encounters with COVID-19 patients accounted for 1 percent of all 911 EMS responses, involving over 1,200 unique COVID-19 patients and thousands of patient-provider encounters during the study period. An estimated 16 percent of the encounters involved treatment with AGPs. However, of the 30 COVID-19 cases among EMS providers, 29 were not related to COVID-19 patient encounters.

Overall, the team found that the COVID-19 incidence among EMS providers was 0.57 infections per 10,000 person-days, which is considered low-risk.

" 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 researchers explained in the study.

Hence, mitigation strategies and the use of PPE can effectively protect against contracting SARS-CoV-2 during emergency patient care.

Journal reference:

Brown, A., Schwarcz, L., Counts, C. et al. (2021). Risk for Acquiring COVID-19 Illness among Emergency Medical Service Personnel Exposed to Aerosol-Generating Procedures. U.S. Centers for Disease Control and Prevention (CDC) Emerging Infectious Diseases.,
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Re: Aerosolized Transmission

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Strategies to reduce SARS-CoV-2 infection risk from bioaerosol exposure during dental procedures

8/3/21 ... dures.aspx

Limiting infection transmission is central to the safety of all in dentistry, particularly during the current SARS-CoV-2 pandemic, yet many dental procedures unavoidably generate aerosols. In the study "Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2," published in the Journal of Dental Research (JDR), researchers at the University of Leeds, England, UK used a 'phantom head' model to mimic dental procedures in a multifaceted approach to measure aerosol dispersal in a dental surgery setting and determine the potential of different mitigation strategies to reduce the infection risk to the dental team from bioaerosol exposure during routine dental procedures.

In a dental surgery setting, crown preparation and root canal access procedures were performed with an air turbine or high-speed contra-angle hand-piece (HSCAH) operated with water cooling, with mitigation via rubber dam or high-volume aspiration and a no mitigation control. A phantom head was used with a flow of artificial saliva infected with Φ6-bacteriophage, a surrogate virus for SARS-CoV-2. Bioaerosol dispersal was measured using agar settle plates lawned with the Φ6-bacteriophage host, Pseudomonas syringae. Viral air concentrations were assessed by active air sampling, and particle size and quantities were monitored using optical particle counters.

Bioaerosol levels were clearly diminished when using the HSCAH compared with the air turbine. Use of rubber dam or high volume evacuation were also effective in reducing bioaerosols and splatter.

While this model represents a worst-case scenario for possible SARS-CoV-2 dispersal, these data showed that the use of HSCAHs or other mitigation strategies can vastly reduce the risk of viral aerosolization, and suggests a prolonged clinic fallow time is not necessary.

" It is imperative to understand the inherent risks of viral dispersion associated with dental procedures and the efficacy of available mitigation strategies. To our knowledge, this study is the first to report the aerosolization in a simulated dental setting of bacteriophage, as a surrogate for SARS CoV2, as a marker for risk determination. The data described here present a clear picture of how risk of SARS-CoV-2 and similar biological hazards can be greatly attenuated using mitigation strategies including HSCAHs."

- Nicholas Jakubovics, JDR Editor-in-Chief, Newcastle University, England


International & American Associations for Dental Research

Journal reference:

Vernon, J.J., et al. (2021) Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2. Journal of Dental Research.
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Re: Aerosolized Transmission

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Study conducts systematic review of the pre- and asymptomatic SARS-CoV-2 transmission

8/3/21 ... ssion.aspx

The rapid outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) across the world has led to a pandemic which is popularly known as coronavirus disease 2019 (or COVID-19). SARS-CoV-2 is a highly infectious RNA virus that has a very high rate of transmission and causes mild to severe infection.

To date, this virus has claimed more than 4.2 million lives worldwide. The main aim of the World Health Organization’s (WHO) Global Strategic Preparedness and Response Plan for COVID-19 disease is to prevent further transmission of the virus and, thereby, aim to reduce the mortality rate owing to this disease.


Previous systematic reviews had mainly shown the methodological shortcomings of the available studies associated with SARS-CoV-2 infection dynamics. These studies failed to draw any firm conclusions about the COVID-19 transmission dynamics. Further, a very limited number of studies are available that explain the transmission dynamics of the SARS-CoV-2 virus (i.e., the transmission of the infection from one infected person to another healthy individual). Hence, there is a gap in research regarding the understanding of transmission dynamics of COVID-19 disease in the individuals who develop symptoms post-testing (presymptomatic) or are asymptomatic.

Scientists have stated that to develop standardized methods to determine the transmission dynamics of SARS-CoV-2, an amalgamation of clinical, epidemiologic, molecular, and laboratory evidence should be brought together into the framework. The studies associated with this framework must contain high-quality confirmatory evidence, such as viral culture, genome sequencing, etc., which would indicate the infectivity of the virus.

A new study

Researchers at Oxford University, UK, have conducted a systematic review of the available studies to address a) whether asymptomatic or presymptomatic individuals can transmit the disease; b) the duration of the infectiousness of these individuals (asymptomatic or presymptomatic); c) the relationship between infectiousness and PCR cycle threshold; and d) whether a chain of transmission can arise from asymptomatic and/or presymptomatic individuals with SARS-CoV-2 infections. The team’s paper detailing their review’s findings has been made available on the medRxiv* preprint server, while it undergoes peer review.

The study surveyed relevant articles from LitCovid, medRxiv, Google Scholar, and the WHO Covid-19 databases. The researchers of this study have included all studies from March 31, 2021, and also included the lists of references therein. They included studies related to people who were exposed to SARS-CoV-2 infected communities or individuals, within 2-14 days of their infection.

The researchers identified 18 studies from a variety of settings that fitted their criteria. As stated above, a limited number of systematic reviews are available that have highlighted the lack of standardized methodology and proper reporting criteria and noted various shortcomings regarding the methodology associated with transmission studies. An interesting factor of this study is that the authors received 100% responses to reviewers’ queries. The authors of the 18 studies included in this study had cooperated immensely by satisfying all the queries with valid data to help standardize the methods associated with viral transmission studies.

Typically, research on transmission dynamics is technically challenging to conduct, especially with an ongoing pandemic. Another difficulty of conducting research on disease transmission lies in identifying asymptomatic patients at the time of the surveys. The current study revealed a high rate of presymptomatic cases that ranges between 50% and 100% in nursing homes or care home facilities.

Among the 18 studies, the researchers classified 15 studies in the category of high risk of COVID-19, and the remaining 3 were categorized as moderate risk studies. The team reported that among the high-risk studies, it is extremely difficult to differentiate between presymptomatic and asymptomatic cases. Owing to scarce data, determining the duration of infectiousness of the infected individuals with asymptomatic (6 studies) or presymptomatic (4 studies) could not be confirmed. Only three studies were found that provided possible evidence on asymptomatic transmission of COVID-19.

Similarly, the researchers found five highly cited studies that provided evidence on presymptomatic transmission of SARS-CoV-2. Previous studies have reported the challenges faced to evaluate the COVID-19 symptom profile of older adults, showing a need for more thorough studies associated with clinical observations that could provide an accurate classification of clinical symptoms.


The researchers stated that single or point binary PCR testing does not provide much information regarding the transmission rate of the disease. A follow-up study with repeated PCR tests in precise intervals could help understand the transmission of the disease. Typically, the Ct (cycle threshold) values represent the probability of the number of times the virus can undergo replication.

The team found insufficient data on the connection between virus transmission and the age of patients. They found that a variable percentage of asymptomatic candidates might develop symptoms later.

The team stated that more research must be conducted to gain a better understanding of the roles of asymptomatic and presymptomatic individuals in the transmission dynamics of SARS-CoV-2. Additionally, the researchers have recommended more longitudinal follow-up studies for at least three weeks with detailed epidemiological reports.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Jefferson, T. et al. (2021). Transmission of SARS-CoV-2 from pre and asymptomatic infected.medRxiv 2021.07.28.21261254; doi:, ... 21261254v1.
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Re: Aerosolized Transmission

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SUSU scientists conduct CFD study to monitor the spread of respiratory viruses in enclosed areas

8/27/21 ... areas.aspx

Scientists from the South Ural State University (SUSU) have conducted a CFD Study for monitoring the spread of respiratory viruses in closed spaces. According to the researchers, the new development will prevent the spread of COVID-19 and other viral infections in spaces where people study or work like educational institutions or offices. The results were published in the Journal of Hazardous Materials.

Respiratory viral infections are transmitted from person to person primarily through airborne droplets as a result of direct or indirect contact. Distances between people in closed spaces do not always provide protection against viruses due to air circulation. That is why the proper positioning of barriers is one of the most effective ways to reduce the spread of respiratory viruses in enclosed areas.

The SUSU scientist has conducted a CFD (Computational Fluid Dynamics) study that allows to analyze droplet flows in the air and to determine the effective location of barriers protecting people in a room.

"The approach of CFD is a combination of computer codes and programs that allows the simulation of different physical and chemical processes. It is used in almost all areas of research, while CFD itself is applied in a wide range of scientific fields – from supersonic aviation to bio-energy and others. The study simulates the real situation in classrooms as accurately as possible."

- Afrasyab Khan, Senior Researcher of the Department of Hydraulics and Hydro-pneumatic Systems, Polytechnic Institute, SUSU

According to him, thanks to the CFD, enterprises will be able to maintain a normal pace of work and avoid quarantine during adverse epidemiological situations.

" This study is a starting point for detailed examination of various scenarios by using the theoretical and experimental approaches. Cooperation is planned at both national and international levels."

- Afrasyab Khan, Senior Researcher

In the future, the scientists plan to develop the strategy based on such CFD studies through which in different scenarios like offices, railway stations, airports, harbors, and factories, SOP's will be established to work without shutting the operations down.


South Ural State University

Journal reference:

Mirzaie, M., et al. (2021) COVID-19 spread in a classroom equipped with partition - A CFD approach. Journal of Hazardous Materials.
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Re: Aerosolized Transmission

Post by trader32176 »

Study reveals measures to tackle musical COVID-19 transmission

8/28/21 ... ssion.aspx

As the COVID-19 pandemic swept the globe in 2020, musicians around the world were desperate for the answers to two pressing questions: Can playing musical instruments transmit COVID-19? And if so, what can be done?

Now, halfway through 2021, the first official research results are in-;and it's good news: The show can go on.

Published today in the journal ACS Environmental Au, University of Colorado Boulder and University of Maryland researchers have found that while playing musical instruments can emit the same levels of potentially COVID-laden airborne particles as singing, simple safety measures, such as masking instruments, social distancing and implementing time limits, significantly reduce this risk.

" COVID has shown people that aerosol transmission of respiratory diseases is something that happens. But just because it goes into the air doesn't mean that everyone is going to contract this disease. We found that there are ways to mitigate these aerosols in a space and ways to reduce your risk."

- Tehya Stockman, Study Lead Author and Graduate Student, Mechanical Engineering, University of Colorado at Boulder

This research began in earnest in 2020 at CU Boulder and the University of Maryland to find out if playing musical instruments carried the same risks of COVID-19 transmission as singing is shown to have. While there have been no reported outbreaks from instrumental ensembles, these published findings echo the researchers' initial hypotheses and recommendations that were eagerly accepted early on in the pandemic by musicians and performing groups worldwide.

"I want to acknowledge the courage of the music directors and the teachers to go ahead and follow our suggestions in the face of all of this adversity, fear and worry," said Shelly Miller, co-author of the study and professor of mechanical and environmental engineering. "That really meant a lot to us because they trusted our very good research methods, our researchers and the evolution of science as it moves from: we don't know, to, let's find out, to OK-;now we know this."

These findings not only apply to the specific musical applications in which they have been tested, they also further validate that masking works as an effective mitigation technique, and ventilation and social distancing are important to reduce transmission, said Miller. Miller said she hopes these findings will further inspire a paradigm shift focused on mitigation measures and ventilation in order to reduce airborne transmission of infectious diseases.

Mitigation matters

The researchers tested three mitigation strategies on a variety of woodwind, reed and brass instruments, as well as with two singers and an actor. They evaluated these strategies, different lengths of performance time and the differences between indoor and outdoor locations by measuring aerosols, carbon dioxide levels and visualizing the flow of the air using various modeling techniques.

First, they found that masks work-;even on instruments-;and the quality of the filtering material and their fit are important. Masks worn securely over a singer's mouth and nose, as well as bell covers (made of MERV13 filter material) placed over the ends of instruments significantly decreased the speed and amount of particles produced from both sources.

For woodwind and reed instruments, they found that the amount of air that escapes from the keyholes does not significantly contribute to any increased risk. This means that clarinetists and flautists do not have to place a bag around their entire instrument to play safely.

Second, time together matters. To keep risk low (at 10% chance of transmission), instrumentalists should spend less than 30 minutes indoors and less than 60 minutes outdoors playing together at a time. No matter the amount of social distancing, "infection risk continuously increases with the duration regardless of the distance to the singer or the player," the researchers found.

They also found that spacing out does pay off: Leaving several feet of distance between players and singers reduces aerosol concentrations, which are highest closest to each person producing them. And while playing outdoors is best, a layered approach with all the other mitigation measures makes it much safer to play indoors.

Finally, no Plexiglass or face shields are needed. The airborne particles that transmit COVID-19 can easily flow around these barriers and mix with the air in a room.

Quantifying carbon dioxide

So how then, can a musician or audience member now know it's safe to attend a concert?

Carbon dioxide has been shown to be great indicator of how well ventilated-;or not-;an indoor space is, and therefore its level of risk for catching COVID-19.

But in this study, the researchers showed that when somebody wears a mask, carbon dioxide passes through the mask with the air that a person is exhaling, but the particles which can carry the virus get stuck. This means that when someone puts on a mask or a bell cover, the carbon dioxide emissions continue, but the particle emissions (which could carry the virus) are reduced.

"Carbon dioxide concentration is a measure of the ventilation in the room. But if everybody's wearing a mask, the carbon dioxide in that room is still going to be high, but the respiratory droplets that may contain the virus are going to be much lower," Marina Vance, co-author on the study and assistant professor in the Paul M. Rady Department of Mechanical Engineering and the Environmental Engineering Program. "So in that case, it's not a direct representation of your risk."

So, if a concert hall requires all audience members to wear masks and that all performers place a bell cover on their instrument, the risk of COVID transmission in that room would be reduced-;even if the measured carbon dioxide levels are high. But carbon dioxide is still a great proxy for risk indoors in restaurants, where most people are not masked and are often speaking loudly.

Such direct application of this research to real-life scenarios has been an extremely rewarding experience for Vance and the other researchers.

"The best part of the study was that all of this technical knowledge and all of this scientific understanding was getting translated almost in real-time and getting into the hands of the people that needed it the most. I've never been a part of anything like that," said Vance. "It was nerve-wracking, exciting and important all at once."
The safe return of music

When lead author Stockman first learned to play clarinet years ago, she didn't do so with the intent to advance scientific research. But her personal musical experience allowed the work to advance quickly, as she performed calibration tests by herself in the lab during the pandemic.

She understands the frustrations of musicians who may need to follow these protocols. She also knows how important it is to keep people safe.

"What we've shown is that there's easy measures to take that make life still be relatively normal-;and you don't have to fear the air," said Stockman.

This sentiment is echoed by co-authors Mark Spede, national president of the College Band Directors National Association and director of bands at Clemson University, and James Weaver, director of Performing Arts and Sports for the National Federation of State High School Associations, who point out that the mitigation strategies tested in this study can be implemented not only during the lingering COVID-19 pandemic, but in the face of any future pathogen that may come along.

"Although we may not know how the end of the pandemic will play out, this important study has allowed performing arts educators to advocate for the safe return of live music to the classroom," said Spede.


University of Colorado at Boulder

Journal reference:

Stockman, T., et al. (2021) Measurements and Simulations of Aerosol Released while Singing and Playing Wind Instruments. ACS Environmental Au.
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