Aerosolized Transmission

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Aerosolized Transmission

Post by trader32176 »

Evidence of SARS-CoV-2 spreading in an airplane toilet

Aug 30 2020 ... oilet.aspx

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease (COVID-19), is still actively spreading like wildfire, with nearly 300,000 new infections reported daily across the globe. Early on in the outbreak in China, scientists said that the virus could spread through respiratory droplets, when a person coughs, sneezes, or speaks.

Recent evidence shows that the virus can remain suspended in the air and travel long distances as aerosols. Another recent study shows that infectious SARS-CoV-2 aerosols can travel up drain pipes in toilets in buildings and apartments, even reaching several floors above.

Now, a team of researchers says they have evidence that a woman contracted the coronavirus on a flight, perhaps in the airplane’s toilet.

The study, published in the journal Emerging Infectious Diseases, reveals evidence of transmission on an evacuation flight from Milan, Italy, to Seoul, South Korea, in late March.

Evacuation flight

Before boarding the flight, about 300 people were screened for the symptoms of COVID-19. The medical staff performed physical examinations, medical interviews, and body temperature checks outside the airport.

About eleven passengers who had symptoms were removed from the flight, and the medical team, which was dispatched by the Korean Centers for Disease Control (KCDC), were trained in infection control procedures based on the World Health Organization guidelines.

The medical staff provided N95 masks to all the passengers, and they were kept 2 meters apart for physical distancing during the preboarding procedure. During the duration of the flight, all the passengers kept their masks on, apart from mealtimes or when they used the toilet.

After the 11-hour flight, 299 asymptomatic passengers arrived in South Korea and had undergone a 2-week quarantine period. The passengers were brought to a government isolation facility, and they were tested for SARS-CoV-2 by reverse transcription PCR twice, on the first day of the quarantine, and by the 14th day.

Positive patients

Six of the travelers tested positive at the start of the quarantine period but were asymptomatic or had no symptoms of COVID-19. Meanwhile, a seventh passenger tested positive on the seventh day of the quarantine, despite previously getting negative results.

The passenger had worn her N95 mask for the entire flight duration, except when she used the bathroom. She also was seated three rows ahead of the asymptomatic travelers.

“Given that she did not go outside and had self-quarantined for 3 weeks alone at her home in Italy before the flight and did not use public transportation to get to the airport, it is highly likely that her infection was transmitted in the flight via indirect contact with an asymptomatic patient,” the researchers said.

The patient-reported symptoms such as coughing, runny nose, and body pains on the 8th day of quarantine and was transferred to a hospital on the 14th day. The remaining 292 passengers were released from quarantine on the 15th day.

Flight transmission of pathogens

Previous studies have shown that inflight transmission of other respiratory infections, such as severe acute respiratory syndrome (SARS) and influenza, may occur in people who sit near an infected person. This considering the difficulty of airborne infection transmission during the flight due to the high-efficiency particulate-arresting filters used in aircraft ventilation systems.

Usually, the transmission of the virus occurs when passengers are boarding, moving, or disembarking. Meanwhile, the researchers believe the woman contracted the virus in the plane’s toilet.

Since the KCDC performed robust infection control procedures, the woman may have been exposed to the virus in the toilet when an asymptomatic passenger may have used it before she did.

The team also noted that other explanations might indicate that she had previous SARS-CoV-2 exposure; she had a more extended incubation period or had other unevaluated situations where she contracted the virus.

“Our research provides evidence of asymptomatic transmission of COVID-19 on an airplane. Further attention is warranted to reduce the transmission of COVID-19 on aircraft. Our results suggest that stringent global regulations for the prevention of COVID-19 transmission on aircraft can prevent public health emergencies,” the team concluded.

The coronavirus pandemic is sweeping across the globe, with most of the cases tied to asymptomatic spread. With the airborne or aerosol transmission a possibility, many people may get infected if they do not practice infection precautions, such as proper hand hygiene, wearing masks, and physical distancing.
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Aerosolized Transmission

Post by trader32176 »

Protocols for minimizing risk in COVID-19 bronchoscopy

9/3/20 ... scopy.aspx

With the onset and explosive spread of the COVID-19 pandemic, healthcare professionals have come under a lot of scrutiny as well as stress, as they are on the frontline of the battle. One area, discussed in a recent paper by Northwestern University researchers and published on the preprint server medRxiv* in August 2020, is the viral exposure suffered by healthcare workers during bronchoalveolar lavage (BAL). BAL is a diagnostic method of the lower respiratory system in which a bronchoscope is passed through the mouth or nose into an appropriate airway in the lungs, with a measured amount of fluid introduced and then collected for examination.

Aerosols and Viral Spread

The pandemic is thought to be most commonly spread by aerosols containing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One classic aerosol-generating procedure is BAL. As a result, many professional societies have issued guidelines specifying that this should be carried out only when strictly required. However, this overlooks one fundamental flaw: the risk of infection during such procedures is unknown.

BALs for Better Outcomes

The current study exploits the fact that over 450 BALs were carried out on intubated patients with COVID-19 disease, using a modified protocol, to examine the actual risk to the healthcare providers. BALs are typically performed in these situations to diagnose bacterial superinfections in the presence of viral pneumonia, as have been known to occur commonly during influenza pandemics, pushing up mortality rates. The very high rate of death in COVID-19 pneumonia patients with such bacterial co-infections indicates the need for the proper identification and treatment of the latter.

Early studies by the current researchers indicate that bacterial infections are common in these patients, especially when they require mechanical ventilation. BAL and quantitative culture is, therefore, a helpful test for such diagnoses, and has long been part of the protocol in the center that this study focuses on. Here, healthcare providers perform BAL and rapid diagnostic tests to detect and treat severe pneumonia. This also allows them to evaluate the lung microenvironment in this condition.

Protocols for Safety

The standard procedure here is non bronchoscopic BAL, which is carried out by respiratory therapists, with the bronchoscopic variant reserved for difficult cases. The concern with the advent of COVID-19 was the generation of respiratory aerosols, which led to a lower rate of BAL. However, endotracheal aspiration failed to return the same satisfactory results and requires the ventilator to be disconnected for an extended period, which is unacceptable in this clinical setting, leaving bronchoscopic BAL as the only safe option

Little information has trickled down about the safety of these procedures in this scenario, some studies showing the infection rate to be low, while guidelines by professional organizations discourage its routine use in these patients based solely on expert opinion. To help settle the debate, the researchers first set up and then tested out a safety protocol for bronchoscopic BALs in intubated patients with respiratory failure and who have or are suspected of having COVID-19.

The study included 52 staff involved in lung and critical care at a tertiary-level hospital. All the bronchoscopies were carried out by attending pulmonary ICU physicians, or interventional pulmonary physicians or fellows. There were no nurses or respiratory therapists present during the bronchoscopy itself.

All participants wore PPE and used disposable bronchoscopes. The use of a short-acting muscle paralyzing agent cisatracurium was encouraged to discourage coughing during the procedure. Short clamping of the endotracheal tube and brief interruption of the inspiratory limb of the ventilator circuit was recommended to allow proper placement of the bronchoscope. The participants also rated the difficulty of the procedure on a score of 1 to 10.

Satisfactory Results

The researchers received a 90% response rate, with over 40% having spent five weeks on ICU service with patients known or suspected to have COVID-19. The highest number of BALs performed by any single provider on these patients was over 60, and the lowest zero. Approximately 80% had performed one or more bronchoscopies, with the median range being 10-30.

Twelve of the providers reported that they could not follow the modified protocol fully, and two could not don full PPE, the respondents reported. Over 40% spent five or more weeks in ICUs caring for COVID-19 patients, which correlated well with the number of bronchoscopies.

Overall, the difficulty was not significantly greater with this protocol than for a routine BAL in an ICU patient, with the median score being 6. This was not related to the number of bronchoscopies or the time on ICU service.

The respondents perceived these to be safe procedures in their setting, with full precautions and PPE available as required. Almost half of the providers (27) who did these providers had been tested at least once by nasopharyngeal swab (NPS) for the infection, but none were positive, while serology was positive in one of 27. In this case, the individual had been tested twice by serology, and the other test returned a negative test. No symptoms of fever and respiratory illness were present.


Though small and single-center, the study indicates that with proper safety precautions, the risk of COVID-19 transmission to healthcare providers during bronchoscopic BALs is low. The protocol used by providers in this study includes:

Excluding unnecessary staff from the room during the procedure
Preventing aerosol generation by shutting off parts of the ventilator circuit during manipulation
Using appropriate drugs to minimize the risk of coughing
Using single-use scopes

Also, the protocol was largely adhered to because the providers in most cases came from a small group of highly skilled professionals and because the difficulty was not significantly greater compared to routine bronchoscopies in an ICU setting.

The researchers say that since other similar centers are likely to have the same type of protocols, a more systematic exploration of the procedure would help to codify its efficacy in preventing infection. This could lead to the development of medical care protocols in line with scientific evidence and not only medical opinion.

The researchers show that the priority of keeping medical staff safe required them to rule out the previous standard of care non bronchoscopic BAL performed by respiratory therapists. Instead, the providers who already did this procedure as part of their critical care were trusted to do it safely, using PPE and adopting precautions to avoid excessive aerosol generation. This proved to be a valid line of action, they say.

Conclusion and Future Directions

" They point out, “Our group has supported adhering to evidence-based critical care during the COVID-19 pandemic rather than making practice changes solely in response to uncertainties associated with the COVID pandemic.”

The study is limited by its retrospective and recall-based design. Protocol adherence was not monitored. Serology testing was not mandatory, and NPS testing was also based on the likelihood of exposure or symptoms. Asymptomatic infection may have been missed as a result.

However, this report fills a necessary slot as the first in-depth report on the real-time risk of BAL in a large center handling multiple such procedures on COVID-19 patients. More research will be required to shape the best protective protocol and its indications in this pandemic, so as to achieve the best outcomes. However, the current findings suggest, they say, that “BAL can be routinely incorporated into the ICU care of these patients with minimal infectious risk to providers.”
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Aerosolized Transmission

Post by trader32176 »

Individual biocontainment unit protects health care workers against aerosolized SARS-CoV-2 virus

9/4/20 ... virus.aspx

Especially in settings where personal protective equipment, or PPE, is in short supply, intubation -- inserting a breathing tube down a patient's throat -- poses a major risk of SARS-CoV-2 exposure for doctors and nurses as viral particles are released into the air.

Researchers from UPMC and the U.S. Army Combat Capabilities Development Command's Army Research Laboratory (CCDC-ARL) created an individual biocontainment unit, or IBU, to keep front line health care workers safe while they provide life-saving care. The device is described in a study published today in the Annals of Emergency Medicine.

Earlier attempts to minimize exposure to health care workers involved placing a plexiglass intubation box over a patient's head and shoulders. Clinicians slip their hands through two large holes in the box to intubate the patient inside. While such a device may contain the worst of the splatter, it can't keep aerosols from leaking out.

The IBU is designed to suck contaminated air out of the box with a vacuum and trap infectious particles in a filter before they seep into the room.

Simulating a COVID-19 patient, the researchers placed a mannequin inside the IBU as well as in a commercially available intubation box. Near its mouth, they piped in an oil-based aerosol which formed tiny droplets in the air, similar in size to the SARS-CoV-2 particles in breath that spread COVID-19.

The IBU trapped more than 99.99% of the simulated virus-sized aerosols and prevented them from escaping into the environment. In contrast, outside of the passive intubation box, maximum aerosol concentrations were observed to be more than three times higher than inside the box.

" Having a form of protection that doesn't work is more dangerous than not having anything, because it could create a false sense of security."

- David Turer, M.D., M.S., study co-lead author, plastic surgeon who recently completed his residency at UPMC

Because of concerns about the potential of airborne viruses to leak from the plexiglass boxes, the Food and Drug Administration (FDA) recently revoked their Emergency Use Authorization (EUA) for these enclosures.

Several months ago, Turer and colleagues submitted an EUA application for the IBU and are preparing to manufacture the devices for distribution.

"It intentionally incorporates parts from outside the medical world," said Turer, who now is at the University of Texas Southwestern Medical Center. "So, unlike other forms of PPE, demand is unlikely to outstrip supply during COVID-19 surge periods."

Besides protecting providers during intubation, the IBU also can provide negative pressure isolation of awake COVID-19 patients, supplying an alternative to scarce negative pressure hospital isolation rooms, as well as helping isolate patients on military vessels.

"The ability to isolate COVID-19 patients at the bedside is key to stopping viral spread in medical facilities and onboard military ships and aircraft," said study co-lead author Cameron Good, Ph.D., a research scientist at the CCDC-ARL.

Devices similar to IBUs were first used in practice by military personnel in the Javits Center field hospital in New York City when local hospitals were overrun with COVID-19 patients during the first wave of the pandemic.

Once the EUA is granted, hospitals and military units will be able to use the IBU to protect health care workers caring for COVID-19 patients.
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Aerosolized Transmission

Post by trader32176 »

Warm weather increases human mobility, and SARS-CoV-2 transmission

9/9/20 ... ssion.aspx

There have been several studies showing that with human coronaviruses other than the SARS or SARS-CoV-2 pathogens, the virus persists for shorter periods in warmer weather than in other conditions. A recent study published on the preprint server medRxiv in September 2020 shows that the effect of climatic factors such as temperature and humidity is mediated mostly through human mobility. Thus, human behavioral changes are still the mainstay of containment rather than hoping for weather conditions to keep the virus at bay.

Earlier Research

Some earlier papers support a seasonal pattern for the COVID-19 pandemic, especially since the earlier viruses have shown similar stability characteristics in the laboratory setting. Again, prior research shows that the virus rapidly becomes unviable in hotter, more humid climates, which has caused the epidemic curve to appear quite different in tropical and subtropical countries as well. The virus has been shown to spread more rapidly in cold, dry conditions.

This has given rise to quite a few studies which model or estimate seasonal changes in viral transmission based on the temperature in various cities. Some have produced firm conclusions that climate may be of marginal significance. On the other hand, recent empirical studies have been completed, which support earlier projections of the adverse effects of warmth and humidity on virus survival. However, the evidence is still insufficient for any firm conclusions to be drawn.

Viral Transmission Maximum in Cold, Dry Places?

As of now, dry cold regions where the temperature is between 40 and 50 degrees Fahrenheit may be responsible for greater viral spread, the largest reduction being by 30% to 40% at temperatures above 25 degrees. However, even this reduction is inadequate to arrest the exponential spread of the virus, and such temperatures are found in only some parts of the world. Thus, most outbreaks are seen to form in cold and dry areas all over the world.

Nonetheless, the link between temperature variations and the inhibition of the spread of COVID-19 appears to be weak.

The researchers comment, “Even if one assumes that SARS-CoV-2 is as sensitive to climate as other seasonal viruses, summer heat still would not be enough right now to slow down its rapid initial spread through the human population.”

Some other studies show that the number of daily deaths is related to the diurnal range of temperature, as well as the number of cases and the mean temperature. However, there is no proof that the case count reduces when the temperature rises. In fact, some have raised doubts as to the existence of such a relationship between virus survival and high temperature and humidity.

When adjusted for variables such as population size, population density, and the expenditure on health during January to March, the results still showed that the highest growth of the pandemic was in the temperate regions of the Northern Hemisphere, when the mean temperature was 5 degrees Celsius, with a specific humidity of 4-6 g/m3.

Wind, Rain, and Solar Radiation

Other climate factors like solar radiation, wind factors, and rain have not been well studied in this regard. However, the presence of rain and wind typically pushes up the rate of transmission, perhaps not due to viral factors but because people tend to stay indoors. One study found that exposure to ultraviolet radiation in sunlight had a U-shaped relationship with the transmission rate. This would mean that temperate climate zones would experience a drop in the viral spread during summer. Still, in tropical countries, the transmission would go up because of the very intense ultraviolet exposure at these times. Some other researchers have shown that ultraviolet exposure is beneficial in hindering the pandemic.

The wind speed could carry respiratory droplets for much farther distances, but could also impair the stability of the droplet and the survival of the virus, which would lead to reduced transmission. In Turkey, for instance, the wind speed with a 14-day lag, that is, as recorded 14 days before the case count of interest, showed a positive association, and this correlation is supported by some other researchers, but not by all.

Mobility Mediates Effects of Climate

The current study by a French research team finds that climate has a nonlinear effect on the viral spread, modulated by mobility, which is influenced by climatic conditions. Temperature and humidity, when examined singly, affect the case and fatality counts much less when appropriate 28-day lags are used to allow the effects of infection to appear. When all climate-related factors are modeled together, temperature and ultraviolet radiation have the strongest correlation with the pandemic.

The ultraviolet radiation was found to have an inverted U-shaped relationship with cases; only at very high levels of radiation will cases be significantly reduced.

However, when an interactive model is used, temperature, humidity, and solar radiation have strong combined negative correlations with cases and fatalities. Still, warm sunny days encourage mobility, which partly cancels out the reduction in fatality rate caused by climate factors. On the other hand, favorable temperatures reduce indoor crowding and may reduce transmission in this way.

Rather than using straightforward findings such as an increasing fatality rate with increasing mobility, and a higher case rate associated with lower mobility, it is necessary to control for reverse causation and other confounding factors. For instance, as the number of cases increases, restrictions on mobility are likely to come into play. And as lockdowns are implemented, the fatality rate comes down but over a different timescale. Thus, such factors must be taken into account.

Again, mobility will push up the number of infections in a seven-day period of sunshine, with the sunshine strengthening this effect. With a 28-day lag being applied to detect fatalities stemming from this exposure, however, the effect is more significant. This reflects the greater ability of the latter parameter to capture the change in the pandemic with the weather.

The researchers point out, “Increasing individual mobility is a factor of virus spread: when more people are more mobile, the social distancing is likely to be reduced and the transmission rate to increase.”

Policy Implications

The primary channels through which climate factors lead to alterations in the viral transmission rate are, therefore physical, and mediated by human behavior, mainly mobility. Thus, the hottest summers are likely to add only a little to the positive effects of strict physical distancing, especially since while the hot weather and solar radiation reduce viral fitness, social distancing is likely to be neglected as well as hand and face hygiene. Thus, such seasons will call for measures like mask-wearing and social distancing to be implemented more stringently.
Implications for Future Research

The researchers call for more work on air quality and pollution as other modifying factors on climate-related risk in the current model. Pollution, for instance, is known to increase the intensity of the virus. A more holistic view would lead to recommendations embracing the need to forswear unsustainable human activity, mitigate climate change, and other broad-based action to prevent interspecies transmission of such novel pathogens and thus forestall future pandemics.
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Aerosolized Transmission

Post by trader32176 »

Making gyms safer: Why the virus is less likely to spread there than in a bar

9/11/20 ... a-bar.aspx

After shutting down in the spring, America’s empty gyms are beckoning a cautious public back for a workout. To reassure wary customers, owners have put in place — and now advertise — a variety of coronavirus control measures. At the same time, the fitness industry is trying to rehabilitate itself by pushing back against what it sees as a misleading narrative that gyms have no place during a pandemic.

In the first months of the coronavirus outbreak, most public health leaders advised closing gyms, erring on the side of caution. As infections exploded across the country, states ordered gyms and fitness centers closed, along with restaurants, movie theaters and bars. State and local officials consistently branded gyms as high-risk venues for infection, akin to bars and nightclubs.

In early August, New York Gov. Andrew Cuomo called gym-going a “dangerous activity,” saying he would keep them shut — only to announce later in the month that most gyms could reopen in September at a third of the capacity and under tight regulations.

New York, New Jersey and North Carolina were among the last state holdouts — only recently allowing fitness facilities to reopen. Many states continue to limit capacity and have instituted new requirements.

The benefits of gyms are clear. Regular exercise staves off depression and improves sleep, and staying fit may be a way to avoid a serious case of COVID-19. But there are clear risks, too: Lots of people moving around indoors, sharing equipment and air, and breathing heavily could be a recipe for easy viral spread. There are scattered reports of coronavirus cases traced back to specific gyms. But gym owners say those are outliers and argue the dominant portrayal overemphasizes potential dangers and ignores their brief but successful track record of safety during the pandemic.

A Seattle gym struggles to comply with new rules and survive

At NW Fitness in Seattle, everything from a set of squats to a run on the treadmill requires a mask. Every other cardio machine is off-limits. The owners have marked up the floor with blue tape to show where each person can work out.

Esmery Corniel, a member, has resumed his workout routine with the punching bag.

“I was honestly just losing my mind,” said Corniel, 27. He said he feels comfortable in the gym with its new safety protocols.

“Everybody wears their mask, everybody socially distances, so it’s no problem here at all,” Corniel said.

There’s no longer the usual morning “rush” of people working out before heading to their jobs.

Under Washington state’s coronavirus rules, only about 10 to 12 people at a time are permitted in this 4,000-square-foot gym.

“It’s drastically reduced our ability to serve our community,” said John Carrico. He and his wife, Jessica, purchased NW Fitness at the end of last year.

Meanwhile, the cost of running the businesses has gone up dramatically. The gym now needs to be staffed round-the-clock to keep up with the frequent cleaning requirements, and to ensure people are wearing masks and following the rules.

Keeping the gym open 24/7 — previously a big selling point for members — is no longer feasible. In the past three months, they’ve lost more than a third of their membership.

“If the trend continues, we won’t be able to stay open,” said Jessica Carrico, who also works as a nurse at a homeless shelter run by Harborview Medical Center.

Given her medical background, Jessica Carrico was initially inclined to trust the public health authorities who ordered all gyms to shut down, but gradually her feelings changed.

“Driving around the city, I’d still see lines outside of pot shops and Baskin-Robbins,” she said. “The arbitrary decision that had been made was very clear, and it became really frustrating.”

Even after gyms in the Seattle area were allowed to reopen, their frustrations continued — especially with the strict cap on operating capacity. The Carricos believe that falls hardest on smaller gyms that don’t have much square footage.

“People want this space to be safe, and will self-regulate,” said John Carrico. He believes he could responsibly operate with twice as many people inside as currently allowed. Public health officials have mischaracterized gyms, he added, and underestimated their potential to operate safely.

“There’s this fear-based propaganda that gyms are a cesspool of coronavirus, which is just super not true,” Carrico said.

Gyms seem less risky than bars. But there’s very little research either way

The fitness industry has begun to push back at the pandemic-driven perceptions and prohibitions. “We should not be lumped with bars and restaurants,” said Helen Durkin, an executive vice president for the International Health, Racquet & Sportsclub Association (IHRSA).

John Carrico called the comparison with bars particularly unfair. “It’s almost laughable. I mean, it’s almost the exact opposite. … People here are investing in their health. They’re coming in, they’re focusing on what they’re trying to do as far as their workout. They’re not socializing, they’re not sitting at a table and laughing and drinking.”

Since the pandemic began, many gyms have overhauled operations and now look very different: Locker rooms are often closed and group classes halted. Many gyms check everyone for symptoms upon arrival. They’ve spaced out equipment and begun intensive cleaning regimes.

Gyms have a big advantage over other retail and entertainment venues, Durkin said, because the membership model means those who may have been exposed in an outbreak can be easily contacted.

A company that sells member databases and software to gyms has been compiling data during the pandemic. (The data, drawn from 2,877 gyms, is by no means comprehensive because it relies on gym owners to self-report incidents in which a positive coronavirus case was detected at the gym, or was somehow connected to the gym.) The resultant report said that the overall “visits to virus” ratio of 0.002% is “statistically irrelevant” because only 1,155 cases of coronavirus were reported among more than 49 million gym visits. Similarly, data collected from gyms in the United Kingdom found only 17 cases out of more than 8 million visits in the weeks after gyms reopened there.

Only a few U.S. states have publicly available information on outbreaks linked to the fitness sector, and those states report very few cases. In Louisiana, for example, the state has identified five clusters originating in “gym/fitness settings,” with a total of 31 cases. None of the people died. By contrast, 15 clusters were traced to “religious services/events,” sickening 78, and killing five of them.

“The whole idea that it’s a risky place to be … around the world, we just aren’t seeing those numbers anywhere,” said IHRSA’s Durkin.

A study from South Korea published by the Centers for Disease Control and Prevention is often cited as evidence of the inherent hazards of group fitness activities.

The study traced 112 coronavirus infections to a Feb. 15 training workshop for fitness dance instructors. Those instructors went on to teach classes at 12 sports facilities in February and March, transmitting the virus to students in the dance classes, but also to co-workers and family members.

But defenders of the fitness industry point out that the outbreak began before South Korea instituted social distancing measures.

The study authors note that the classes were crowded and the pace of the dance workouts was fast, and conclude that “intense physical exercise in densely populated sports facilities could increase the risk for infection” and “should be minimized during outbreaks.” They also found that no transmission occurred in classes with fewer than five people, or when an infected instructor taught “lower-intensity” classes such as yoga and Pilates.

Public health experts continue to urge gym members to be cautious

It’s clear that there are many things gym owners — and gym members — can do to lower the risk of infection at a gym, but that doesn’t mean the risk is gone. Infectious disease doctors and public health experts caution that gyms should not downplay their potential for spreading disease, especially if the coronavirus is widespread in the surrounding community.

“There are very few [gyms] that can actually implement all the infection control measures,” said Saskia Popescu, an infectious disease epidemiologist in Phoenix. “That’s really the challenge with gyms: There is so much variety that it makes it hard to put them into a single box.”

Popescu and two colleagues developed a COVID-19 risk chart for various activities. Gyms were classified as “medium high,” on par with eating indoors at a restaurant or getting a haircut, but less risky than going to a bar or riding public transit.

Popescu acknowledges there’s not much recent evidence that gyms are major sources of infection, but that should not give people a false sense of assurance.

“The mistake would be to assume that there is no risk,” she said. “It’s just that a lot of the prevention strategies have been working, and when we start to loosen those, though, is where you’re more likely to see clusters occur.”

Any location that brings people together indoors increases the risk of contracting the coronavirus, and breathing heavily adds another element of risk. Interventions such as increasing the distance between cardio machines might help, but tiny infectious airborne particles can travel farther than 6 feet, Popescu said.

The mechanics of exercising also make it hard to ensure people comply with crucial preventive measures like wearing a mask.

“How effective are masks in that setting? Can they really be effectively worn?” asked Dr. Deverick Anderson, director of the Duke Center for Antimicrobial Stewardship and Infection Prevention. “The combination of sweat and exertion is one unique thing about the gym setting.”

“I do think that, in the big picture, gyms would be riskier than restaurants because of the type of activity and potential for interaction there,” Anderson said.

The primary way people could catch the virus at a gym would be coming close to someone who is releasing respiratory droplets and smaller airborne particles, called “aerosols,” when they breathe, talk or cough, said Dr. Dean Blumberg, chief of pediatric infectious diseases at UC Davis Health.

He’s less worried about people catching the virus from touching a barbell or riding a stationary bike that someone else used. That’s because scientists now think “surface” transmission isn’t driving infection as much as airborne droplets and particles.

“I’m not really worried about transmission that way,” Blumberg said. “There’s too much attention being paid to disinfecting surfaces and ‘deep cleaning,’ spraying things in the air. I think a lot of that’s just for show.”

Blumberg said he believes gyms can manage the risks better than many social settings like bars or informal gatherings.

“A gym where you can adequately social distance and you can limit the number of people there and force mask-wearing, that’s one of the safer activities,” he said.

Adapting to the pandemic’s prohibitions doesn’t come cheap

In Bellevue, Washington, PRO Club is an enormous, upscale gym with spacious workout rooms — and an array of medical services such as physical therapy, hormone treatments, skin care and counseling. PRO Club has managed to keep the gym experience relatively normal for members since reopening, according to employee Linda Rackner. “There is plenty of space for everyone. We are seeing about 1,000 people a day and have capacity for almost 3,000,” Rackner said. “We’d love to have more people in the club.”

The gym uses the same air-cleaning units as hospital ICUs, deploys ultraviolet robots to sanitize the rooms and requires temperature checks to enter. “I feel like we have good compliance,” said Dean Rogers, one of the personal trainers. “For the most part, people who come to a gym are in it for their own health, fitness and wellness.”

But Rogers knows this isn’t the norm everywhere. In fact, his own mother back in Oklahoma believes she contracted the coronavirus at her gym.

“I was upset to find out that her gym had no guidelines they were following, no safety precautions,” he said. “There are always going to be some bad actors.”
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Aerosolized Transmission

Post by trader32176 »

Coronavirus can spread on airline flights, two studies show

Updated 11:46 PM ET, Fri September 18, 2020 ... index.html

The young woman and her sister had traveled across Europe just as the coronavirus pandemic was taking off there, visiting Milan and Paris before heading to London.

When the woman left London on March 1, she had a sore throat and cough as she boarded a flight home to Vietnam, but no one noticed.
By the time she got off the flight in Hanoi 10 hours later, 15 other people who had been on the plane with her were infected, researchers reported Friday.

This story is one of two published Friday demonstrating how coronavirus can spread on airline flights, and suggesting that simply spacing people out a little will not fully protect them.

In another incident, passengers on a flight from Boston to Hong Kong appear to have infected two flight attendants.
Both cases involved long flights early in the pandemic, before airlines began requiring face masks.

A team from Vietnam tracked down a cluster of cases linked to the flight that arrived in Hanoi from London on March 2.
"A 27-year-old businesswoman from Vietnam, whom we identified as the probable index case, had been based in London since early February," Nguyen Cong Khanh of the National Institute of Hygiene and Epidemiology in Hanoi and colleagues wrote.

"On February 22, case 1 and her sister returned to Milan, Italy, and subsequently traveled to Paris, France, for the yearly Fashion Week before returning back to London on February 25," they wrote in the journal Emerging Infectious Diseases.

At this time, coronavirus was starting to spread fast in Italy but very few cases had been reported in Britain.
The woman boarded a flight to Hanoi on March 1.

"She was seated in business class and continued to experience the sore throat and cough throughout the flight," the researchers added.

She went to a hospital three days after landing and tested positive for the virus. Health officials tracked down 217 passengers and crew who had been on the flight with her and found 12 fellow business class passengers, two economy class passengers and one crew member were also infected.

The investigators said there was no other likely way any of the 15 others could have been infected other than exposure to the sick patient on the flight.

"The most likely route of transmission during the flight is aerosol or droplet transmission from case 1, particularly for persons seated in business class," they wrote.

"We conclude that the risk for on-board transmission of SARS-CoV-2 during long flights is real and has the potential to cause COVID-19 clusters of substantial size, even in business class--like settings with spacious seating arrangements well beyond the established distance used to define close contact on airplanes," Khanh's team wrote.

"As long as COVID-19 presents a global pandemic threat in the absence of a good point-of-care test, better on-board infection prevention measures and arrival screening procedures are needed to make flying safe."
In the second incident, a couple flew from Boston to Hong Kong in business class on March 9. They both exhibited symptoms after they arrived and were diagnosed with coronavirus.

Contact tracing found two flight attendants were also positive for the virus. "The only location where all four persons were in close proximity for an extended period was inside the airplane," Deborah Watson-Jones of the London School of Hygiene & Tropical Medicine and colleagues wrote in a second report in the US Centers for Disease Control and Prevention's Emerging Infectious Diseases journal.

"Genetic sequencing linked all four cases. The near full-length viral genomes from all four patients were 100% identical," Watson-Jones and colleagues wrote.
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Aerosolized Transmission

Post by trader32176 »

CDC updates coronavirus guidelines to recognize airborne spread

9/21/20 ... pread.aspx

The coronavirus disease (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still actively spreading across the globe. The case toll sits at over 31 million infections, and over 960,000 lives lost.

Early on in the pandemic, it was thought that the virus was only spread via respiratory droplets. However, scientific research soon showed it also to be an airborne virus. Now, the U.S. Centers for Disease Control and Prevention (CDC) has updated its guideline, acknowledging that the virus can hang in the air, fueling its spread.

COVID-19 airborne spread

After the World Health Organization (WHO) acknowledged that SARS-CoV-2 could spread through the air in July 2020, the CDC also updated its guidelines for infection prevention. The health agency noted that COVID-19 most commonly spreads between people who are in close contact with each other, within six feet, and through respiratory droplets or small particles, such as those in aerosols, produced when an infected person sneezes, coughs, speaks, breathes, and sings.

Further, SARS-CoV-2 in droplets and aerosols, can be inhaled through the mouth and nose, pass through airways, and reach the lungs, causing infection. Apart from inhaling these droplets, the virus can also spread through contact with droplets that land on surfaces and objects, which can be transferred by touch. When people touch surfaces with the infected droplets, such as doorknobs, handles, and tables, it can cause infection when they also touch their mouth, nose, or eyes.

Airborne transmission may ensue when droplets from an infected person hang in the air and are inhaled by other people. This may occur in closed areas, crowded places, and areas with poor ventilation.

“There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or fitness classes). In general, indoor environments without good ventilation increase this risk,” the CDC said.

The CDC also emphasized how easily the virus can spread from one person to another. SARS-CoV-2 is considered one of the most contagious viral infections, which can quickly spread, more so than influenza. Overall, the virus can be more infectious when an infected person interacts more closely with others over long periods.

The potential for the animal to human transmission of SARS-CoV-2 has also now been recognized by the CDC. However, that risk is considered very low; some cases of people-to-animal transmissions have been recorded. In some situations, the transmission is possible, including infections from dogs and cats. The CDC says, “At this time, there is no evidence that animals play a significant role in spreading the virus that causes COVID-19. Based on the limited information available to date, the risk of animals spreading COVID-19 to people is considered to be low.”

Protecting oneself

Previously, CDC suggested maintaining a social distance of about six feet, regularly disinfecting surfaces, proper hand hygiene, and covering the mouth and nose with a mask when out in public or around others. Now, the agency adds additional recommendations that people stay home and isolate themselves from others when sick. Use air purifiers to help reduce airborne germs in indoor spaces.

“The best way to prevent illness is to avoid being exposed to this virus. You can take steps to slow the spread,” the CDC emphasized.

Aside from these infection preventive measures, the CDC also recommended to maintain social connections and for people to tend to their mental health.

Global spread

Amid the pandemic, many countries have now re-opened to help boost their economies, heavily impacted by the spreading disease. Along with the lifting of restrictions, many cases are being reported across countries, with the United States still reporting the highest number of cases.

The U.S. has more than 6.8 million cases and nearly 200,000 deaths. Meanwhile, India and Brazil follow with more than 5.48 and 4.54 million cases, respectively. Brazil has more than 136,000 deaths, while India reports more than 87,000 deaths.

Russia, Colombia, and Peru report more than 1 million, 768,000, and 765,000 cases. China has reported over 90,000 cases and 4,737 death.
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Aerosolized Transmission

Post by trader32176 »

COVID-19 lockdown measures reduced air pollution in Southeast Asia

9/21/20 ... -Asia.aspx

Since the detection of the first case of COVID-19 disease in Wuhan, China, at the end of 2019, the novel coronavirus has evolved into a global pandemic, with over 31.2 million confirmed cases and over 963,000 deaths across the globe.

In an attempt to contain the spread of the disease, many countries worldwide, including Malaysia and other Southeast Asian (SEA) countries, have enforced lockdowns of varying degrees, which has inadvertently caused some positive changes to the environment.

The evaluation of the decrease in anthropogenic emissions because of COVID-19-related restrictions imposed by governments is critical to determine the impact of the pandemic on pollution and economic growth. A recent study published in the journal Science of The Total Environment analyzes the impact of COVID-19-related lockdown on aerosols and pollutants over the Southeast Asian atmospheric environment.

This study used aerosol optical depth (AOD) measurements from the Himawari-8 satellite, along with tropospheric NO2 column density measurements from Aura-OMI over SEA countries, as well as ground-based measurements of pollution at various stations across Malaysia, so as determine the changes in aerosol and pollutants linked to the shutdown of human and industrial activities.

Aerosol optical depth (AOD) is a measure of the extinction of solar radiation due to light absorption or scattering by atmospheric dust and haze. The aerosols over the SEA region are mainly from urban and industrial emissions such as organics, nitrate, sulfate, and ammonium; black carbon from fossil fuel and biofuel burning; volcanic ash and dust transported from long distances during pre-monsoon forest and vegetation fires. In addition to these, trace amounts of sulfur dioxide (SO2), ammonia (NH3), nitrogen oxides (NOx), and carbon monoxide (CO) gases undergo complex homogeneous or heterogeneous chemical reactions in the atmosphere and release organic and inorganic aerosols.

Lockdown has helped reduce pollution over SEA regions

The study found that the lockdown has caused a notable decrease in AOD over SEA regions and in the pollution outflow over the oceanic regions. It also detected large reductions (~27 - 34%) of tropospheric NO2 over urban agglomerations and nearly 26-31%, 23-32%, 63-64%, 9-20%, and 25-31% reductions, respectively, in PM10, PM2.5, NO2, SO2, and CO in urban Malaysia during the lockdown phase compared to the same periods in years 2018 and 2019. NO2 levels were reduced even more by 64% in the urban areas and by 33–46% in the industrial sites. Lower reductions were recorded for SO2 and CO, while O3 changes were not significant compared to the previous years.

The results showed a significant reduction in AOD over the southern SEA region, including Singapore, Brunei, Malaysia, and the Philippines. In Malaysia, the AOD values over urban and industrial sites showed a notable decrease (~70% and ~40%) between March to April 2020 compared to the same period in 2018 and 2019. In contrast, in the northern SEA region, AODs stayed at very high levels even during the lockdown, because of extensive agricultural burning and forest fires in this area. This was also in agreement with the highest NO2 levels detected in this area.

There were large reductions in NO2 levels (~27%–34%) during the shutdown period in most SEA cities, except for Yangon and Ho Chi Minh. This NO2 reduction was strongly linked with the efforts taken by these countries to restrict the people's movement within and across countries and to control the industrial and business activities.

Some SEA countries, including Malaysia, Brunei, and Singapore, imposed aggressive restrictions such as the prohibition of mass gatherings, border closures, restriction of religious activities, and partial to complete lockdowns by the army, compared to other countries such as Indonesia, Cambodia, Laos, Thailand, Myanmar, and the Philippines that only enacted mild restrictions.

"Continuous monitoring of the pollution levels and future studies will reveal the degree of the pollution re-appearance over major urban areas in Malaysia as well, after the re-opening on the economy," say the authors

The results of this study indicate that the degree of restriction and the regional lockdowns enacted to contain COVID-19 has affected the air pollution over regions with high aerosols and pollutant levels. The apparent benefits of COVID-19-related restriction measures highlight a unique opportunity for changing pollution control policies and climate change mitigation strategies in SEA countries. Also, the assessment of the reductions in major, harmful air pollutants is very important for air quality and climate change studies and health research. These findings also call for a more detailed analysis of the impact of lockdowns on atmospheric pollution in the future.
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Aerosolized Transmission

Post by trader32176 »

UV-C irradiation rapidly inactivates SARS-CoV-2 on surfaces

9/23/20 ... faces.aspx

Researchers at University Hospital Tübingen, Germany, have shown that ultraviolet C (UV-C) irradiation effectively inactivates surface-dried preparations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the agent that causes coronavirus disease 2019 (COVID-19).

Exposing a high titer of surface-dried SARS-CoV-2 to a low dose of UV-C light for just a short time completely reduced the infectivity of the virus.

The application of UV-C light is already an established technique for decontaminating surfaces and has already proven effective against other viruses and bacteria.

It has also recently been shown that SARS-CoV-2 is sensitive to inactivation using this technique. However, the exposure times needed for complete inactivation of the virus were not conducive with the UV-based methods used in large-scale decontamination processes.

Now, Michael Schindler and colleagues have shown that surface-dried SARS-CoV-2 can be inactivated by low-dose UV-C light in a “real-life” setting in as little as 2 seconds using a handheld device.

“UV-C irradiation is a rapid and cost-effective technology to decontaminate surfaces from high-titer SARS-CoV-2,” says the team.

A pre-print version of the paper is accessible on the server bioRxiv*, while the article undergoes peer review.

Rapid, efficient, non-chemical decontamination procedures are urgently needed

As the COVID-19 pandemic continues to sweep the globe, there is an urgent need for rapid, efficient, non-chemical procedures to decontaminate surfaces of the causative agent SARS-CoV-2.

Application of UV-C irradiation is a well-established, safe procedure used for the environmental control of pathogens and has already proved effective at inactivating SARS-CoV-1 as well as other coronaviruses.

Recently, the sensitivity of SARS CoV-2 to inactivation by UV-C irradiation has also been demonstrated.

However, the doses and exposure times needed to inactivate SARS-CoV-2 completely have been in a range that precludes efficient application of UV-based methods for use in large-scale decontamination of surfaces, say Schindler and colleagues.

“One critical question is the suitability of this technology in a ‘real-life’ setting in which the exposure time of surfaces or aerosols should be kept as short as possible to allow for a realistic application, for example, in rooms that need to be used frequently as operating rooms or lecture halls,” writes the team.

What did the researchers do?

Simulating a situation where exhaled droplets or aerosols from infected individuals contaminate surfaces, the team generated a high-titer stock of infectious SARS-CoV-2 and spotted 35uL of this stock (in triplicates) in 6-well plates which were dried for two hours at room temperature.

The plates were then either left untreated or were exposed to five UV-C regimens.

These regimens included inactivation for 60 seconds in a UV-C box designed to disinfect medium-size objects; 2-second UV-C exposure at a distance of either 5 or 20 cm using a handheld disinfection device and, finally, a movement regimen simulating decontamination of surfaces using the handheld UV-C device.

For the latter, the device was moved at a “slow” speed (about 3.75cm per second) and “fast” speed (about 12cm per second) at a distance of 20 cm from the plates.

The UV-C exposure in the box for 60 seconds corresponded to an irradiation dose of 800 mJ/cm²; the 2-second exposure at 5 cm with the handheld device corresponded to 80 mJ/cm² and 2-second exposure at 20 cm corresponds to 16 mJ/cm².

For the “slow” and “fast” moving regimens, the team calculated UV-C irradiation doses of 2.13 mJ/cm² and 0.66 mJ/cm², respectively.

All five UV-C regimens, but not drying, were effective

Drying for two hours did not have any significant impact on SARS-CoV-2 infectivity, suggesting that exhaled virus present in droplets or aerosols retains infectivity on surfaces for at least two hours.

Treatment with UV-C, on the other hand, effectively inactivated the virus under all five exposure regimens.

Strikingly, even the short exposure to an irradiation dose of 0.66 mJ/cm in the fast-moving regimen resulted in a complete reduction of SARS-CoV-2 infectivity.
An easy, rapid, chemical-free decontamination method

The team says the findings show that that SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation.

“Altogether, we establish the effectiveness of UV-C treatment against SARS-CoV-2 in a setting designed to simulate realistic conditions of decontamination,” write the researchers.

“The easy, rapid, chemical-free, and high efficacy of UV-C treatment to inactivate SARS-CoV-2 demonstrates the applicability of this technology in a broad range of possible settings,” they conclude.

*Important Notice

bioRxiv 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.
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Aerosolized Transmission

Post by trader32176 »

Aerosol-based study of COVID-19 risk indoors, and the impact of preventive measures

9/24/20 ... sures.aspx

A recent study published on the preprint server medRxiv* in September 2020 by researchers from the Max Planck Institute for Chemistry and The Cyprus Institute, Climate and Atmosphere Research Center, describes the estimated risk of COVID-19 transmission via aerosols in many different situations, as well as the expected reduction in risk associated with the use of various preventive measures.

Many scientists now consider that COVID-19 spreads through aerosols, containing particles of diameter 5 μm or less, with extended viral survival in the air as well as long periods of suspension of the microdroplets in the air. Respiratory droplets are still considered to be the main route of transmission. During acute COVID-19, viral loads are high, indicating heightened infectivity at this stage.

In common with SARS-CoV, the current virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also appears to undergo indoor superspreading by aerosols. This is supported by the observation that disease spread is 20 times higher indoors relative to outdoors, and by the fact that many earlier viruses, including respiratory syncytial virus (RSV), Middle East Respiratory Syndrome coronavirus (MERS-CoV), and influenza have been shown to spread this way. However, this is a topic of considerable controversy.

Estimation of Indoor Risk due to Aerosolized Virus

The current study presents a versatile and straightforward but easily understandable spreadsheet algorithm that is used to estimate the chances of indoor viral spread through aerosols. The parameters incorporated into the algorithm include the size of the room, the number of people exposed to the virus, the volume of inhaled air, and the characteristics of aerosol generation via breathing, speaking, singing, and the like.

The viral load and infection dose parameters are based on assumptions made from earlier studies. The study focuses on aerosols, leaving droplets spread out altogether. Each case scenario envisages a single infected person in either the presymptomatic phase, which is thought to be highly infectious or with asymptomatic infection, where infectivity is not clearcut.

The researchers define highly infectious to mean 5×108 viral (RNA) copies/mL, as observed in about one in five positive cases.

Two alternative scenarios are considered: in one, the index patient is very infectious, while in the other, a superspreading event occurs either due to a tenfold higher viral load relative to the former index patient or because of extremely high aerosol production.

Office Spread

The researchers assume that with four individuals being present, one the index case to which the others are exposed, the period of high infectivity is two days at 8 hours each. If only passive ventilation is present, there is a 45% and 18% risk of one other being infected, and of individual infection.

The authors clarify, “The individual infection risk equals the fraction of the group that is at risk, thus being increasingly significant with the number of subjects present.”

Under conditions of active ventilation from outside air, both these risks are 2-2.5 times lower, while with the use of face masks, they decline by 7-8-fold. With high-volume HEPA filtering (HEPA), the risk is 8-9-fold lower while it is 40 times less if high-quality masks are worn.

If a superspreading event occurs, 2-3 individuals would be infected, but with active ventilation only 1-2. Individual risk is 4-5 times less with either masks or HEPA ventilation, while high- quality masks bring down the risk 25 times.

These conditions can be replicated in other surroundings of similar size with the same number of people, such as a hospital ward or nursing home room.

Classroom environment

Young children below ten years of age may be less infective, so the researchers decreased the viral load by 10 for this case. The risk of infection is 21%, while for each individual, it is about 1%. For older students, the overall and individual risk is 91% and 10%, respectively.

The risk is reduced with ventilation from outside for a classroom day of six hours, and for older children, it becomes 58%. In this group, the individual risk drops to 1% if face masks are used.

For high-risk individuals in these surroundings, HEPA may drop the individual risk by 9-10 times, and still, more if other measures are used. This is expensive, of course, and may be used only for this group. Superspreaders among either students or teachers may cause a 63% risk of infection, but this is reduced 6-7-fold by active ventilation and mask-wearing, even more, if high-quality masks are used, though this is unrealistic.

Choir practice

Due to the high aerosol emission during singing compared to breathing, a single highly infectious index case can infect 29% of the others, half this number if active ventilation is present, and 9-fold with HEPA. Face masks are not used in this setting.

Superspreaders can result in infection rates of 71% with active ventilation and 29% with HEPA.


Guests at a reception desk speak loudly compared to people in an office or classroom, but the space is usually bigger, and the exposure time is shorter. Without other measures, about 4 infections may be expected from the index case but two in the classroom. Active ventilation and HEPA will progressively reduce this risk by 2.5 to 3 times and 10 times, respectively. Face masks and good-quality masks also reduce the risk.

If a superspreading event occurs, about 34% may be infected, but with active ventilation, 14%, and 9% with HEPA. Unless high-quality masks are used, four or more guests are likely to be infected in all these conditions.

If more ordinary conditions are envisaged, as when alcohol is served, a band is present, and dancing is held, the reception is more of a party, and the risk is correspondingly higher.

Cluster Infections

If only one index case affects many individuals, a cluster of over 10 COVID-19 cases can break out, which usually occurs with superspreading. This must be rapidly prevented from spreading further. A party at a reception may cause cluster infections even without a superspreader. Since face masks are not usually worn at such parties, HEPA may be advisable to contain the spread by 9-fold, to about 3 cases instead of 34, and thus prevent cluster infection.

Though schoolchildren may be less infective, they also spend more time together and tend to speak loudly or shout, which may push up the overall cluster infection risk significantly.


Of course, these parameters need to be adjusted individually, since the aerosol production rate can vary significantly with the viral load, the type of breathing or vocalization, and the duration of exposure. Indoors, asymptomatic, presymptomatic, and mild COVID-19 cases are the primary sources of secondary transmission.

They comment, “Additional scientific research will need time to quantify infection risks and pathways in greater detail. However, by waiting for additional scientific results, valuable time will be lost that could be used to control the pandemic.”

The researchers also glance at the benefits of using masks, especially if they are multi-layered and contain fluffy material, and more during forceful or loud speaking compared to simple breathing.

Concerning prevention of infection, the most effective measures are high-quality masks and HEPA, but in terms of real-life protection, active ventilation and the wearing of face masks are preferable in terms of the cost and the results. High-quality masks are about 5 times more costly than others but are quite unlikely to be used either by choir singers or by party-reception guests.

Still, properly fitted and worn masks, with hygiene measures, represent the best hope, especially if active ventilation mixes room air with outside air, and if HEPA is used. This algorithm can be used to estimate risks. The study ends with an apt quote from De Kai, who said a “mouth-and-nose lockdown is far more sustainable than a full lockdown, from economic, social, and mental health standpoints.”
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