Aerosolized Transmission

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trader32176
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Aerosolized Transmission

Post by trader32176 »

SARS-CoV-2 droplets travel further and last longer than thought, and even more in humid air

8/10/20

https://www.news-medical.net/news/20200 ... d-air.aspx

The ongoing COVID-19 pandemic is spread by respiratory aerosols, in which tiny droplets of saliva and mucus containing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are expelled from the upper respiratory tract. Though quite a few studies have investigated the viral load of such droplets, not much is known about how far these droplets move or how long they linger in the air, even though such information is crucial to determining how infectious they are.

Now, a new study by researchers at the University of Twente and University of Rome Tor Vergata and published on the preprint server medRxiv* in August 2020 shows that earlier assumptions about these droplets were wrong. In fact, under 50% relative humidity, the smallest droplets survive 50 times longer, and at 90% relative humidity, up to 150 times longer. In other words, the two-meter or six-foot social distancing rule is grossly inadequate, given the actual advective range of the droplets within one second. And the range, as well as lifetime of the droplet, only increases with smaller droplet size.

Preventing Respiratory Transmission

The current rules of social distancing originated with a 1919 paper dealing with the Spanish flu of that time. This, in turn, was based on a theory of droplet transmission of viruses developed by William F. Wells in connection with the spread of tuberculosis. He thought that the wide range of particles produced by a cough or sneeze in a tuberculosis patient would determine the behavior of the droplets. Small droplets would rapidly evaporate and leave behind less infectious dried aerosol particles with lower transmission risk. Larger droplets would be like bullets. In the current study, droplets measuring over 5-10 micrometers are called respiratory droplets and can cause host-to-host spread. Small droplets, or respiratory droplets, transfer the virus through aerosols.

Despite the age of this principle, the evidence is building that it is faulty. Not only has viral spread continued to take place, especially with superspreaders, but the droplets are known to last longer and spread farther than a few seconds and two meters – namely, up to 8 meters and for up to 10 minutes, respectively. This is because droplets are typically expelled as a cloud, within warm and humid air, which delays their drying out and prolongs their infectious period. In fact, droplet lifetime is dependent on the mixing process within this turbulent air, while the earlier drying behavior is that of a single droplet.

Airborne transmission

This change in fundamental assumptions is supported by empirical studies, medical knowledge, and physics – "long-distance airborne transmission through multiphase turbulent droplet cloud emission is an essential factor." Some researchers have shown that very infectious patients may spread the virus in their aerosols over large distances. In fact, the results of such spread may be even more severe disease due to the tiny droplets of the aerosol, which leads to their entry deep into the lungs.

Humidity and Infectiousness

The current study deals not only with the accumulating nature of aerosols, which remains infectious indoors over hours but also with the little-understood contribution of humidity. Because of the immense difficulty in tracing the movement of thousands of tiny droplets in space and over time, while simultaneously keeping track of or adjusting the conditions such as flow rate, distribution width of the droplets, temperature and relative humidity, the researchers chose to use numerical simulations instead.

Assessing Small Scale Droplet Physics

They tweaked existing methods to ensure that the small scale of the droplet mixing process, as well as the coupling of temperature and humidity, which are so essential to the evaporation of the droplets and thus their lifetime and effects, are properly captured. This involved the development of a very efficient numerical tool that will be of use in revealing the flow physics of an event occurring with breathing, and also what decides the enormous enhancement of the lifetime of a respiratory droplet relative to considering the droplet isolated from its surrounding puff velocity, temperature, and humidity. This tool can also be used to simulate more complicated respiratory events, especially those which take place indoors.

The conditions of the experiment included a duration of 0.6 seconds, simulating a turbulent puff of air into ambient air, full of 5,000 droplets of water, as well as hot air saturated with vapor, in order to replicate a strong cough. The initial temperature was 34 oC. The temperature of the ambient air was set at 20oC, with the relative humidity between 50% and 90%. The heat and vapor in the turbulent puff are exchanged to the ambient air. The researchers tracked the droplets for several seconds to understand the physics underlying their evaporation en masse.

Fall Pattern of Large and Small Particles

The first result at a RH of 50% is the falling out of larger droplets over 100 μm in diameter, in a ballistic manner, because of their weight compared to the airflow, at 0.1 m to 0.7 m from the source. These evaporate faster, compromising the survival of the infectious particles. This agrees with the earliest predictions (Wells, 1930), and the current social distancing guidelines by the World Health Organization (WHO), Center for Disease Prevention and Control (CDC) and the European Centre for Disease Prevention and Control (ECDC).

When smaller than this, however, the droplets form spirals tracing a mostly horizontal path, which means they also promote airborne rather than droplet transmission – unlike the current WHO hypothesis. This is due to their slower settling speed compared to the velocity of the fluid in which they are carried, which means further advection by the turbulent airstream. This latter is essential in airborne transmission of infection.

This small droplet behavior means they have much higher lifetimes than isolated droplets. In fact, 10 μm droplets at RH 50% and 90% have 60 to 200 times the survival times of the Wells value. These move slower related to the fluid flow, and so shrink less due to reduced convection and evaporation.

With successive coughs, therefore, the puff may reach over 2 m from the source at the leading edge, with most of the smaller droplets being in humid surroundings and thus living longer.

Implications and Recommendations

Thus, the study shows that the humidity field around the droplet plus the turbulent velocity, and not just the droplet diameter, determines the respiratory droplet lifetime. This boosts their lifetime by orders of magnitude. The ambient RH further extends the lifetime, and the researchers comment, "This finding may explain why many COVID-19 superspreading events have been reported in indoor environments with large ambient relative humidity." They quote the high spread in meat-processing plants with cooled air, which increases the indoor RH immensely.

This means that aerosol and droplet concentration must be controlled indoors, especially in the coming fall and winter. Again, older medical experts like Soper (1919) are proved right with their claim, originally pertaining to the Spanish flu pandemic of those years, that "there is danger in the air in which they cough and sneeze." Even further, according to the current study, "we must also add "speak," "sing," scream," and even "breath." In fact, Soper recommended open windows at home and work, and masks for suspected patients – an excellent protocol for today at well.

The current study thus confirms and explains Soper's mitigation strategies for use in controlling COVID-19 transmission. The researchers say face masks block respiratory droplets indoors, and some may even reduce the inhalation of these droplets, an essential role for healthcare workers in the pandemic.

Excellent ventilation is equally important to ensure the infectious puff advects out of the room or becomes rapidly and highly diluted. A possible unfavorable effect of this is that good ventilation may increase the length of the propagation path of the droplets, and these two effects of ventilation on transmission properties must be investigated in parallel.

Finally, a lower ambient RH will help speed up the evaporation of the droplets and aerosols, reducing infectivity by decreasing the lifetime of infectious particles and aerosols.

The study sums up, "Our results help to understand why these various mitigation strategies against COVID-19 are successful…. Our present tool and approach will be a starting point for larger parameter studies and for further optimizing mitigation strategies ."
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TimGDixon
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Re: SARS-CoV-2 droplets travel further and last longer than thought, and even more in humid air

Post by TimGDixon »

Good read Trader - keep in mind that Sars/CoV2 is not a living organism but a protein and it is quite fragile at the same time - best to keep safe distances from people until you yourself have been infected or received a vaccine to induce immunization - better yet keep up your maintenance dose of QM to keep your immune system in a state of vigilance.
trader32176
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Joined: Fri Jun 26, 2020 5:22 am

Aerosolized Transmission

Post by trader32176 »

Study shows coronavirus thrives in dry air with low humidity

8/18/20

https://www.news-medical.net/news/20200 ... idity.aspx

Viral infections like influenza or flu are seasonal, and the common cold is more likely in winter. Now, scientists wonder if the novel coronavirus spreads more easily under specific climatic conditions.

A new study by researchers from the University of Sydney and the Fudan University School of Public Health in Shanghai suggests that low humidity increases the risk of spreading the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Climatic factors of COVID-19 spread


The global spread of SARS-CoV-2, the virus that causes the coronavirus disease (COVID-19), has been tied to climatic factors, which have a biological basis. Generally, the spread of SARS-CoV-2 among people is through respiratory droplets and aerosols, and possibly fecal-oral routes.

Further, previous studies have shown that temperature and relative humidity can affect the spread of SARS-CoV-2 through virus survival, wherein they thrive longer in lower temperatures, and the length of time infectious respiratory matter stays suspended in the air. In lower humidity, more virus material stays suspended for longer.

Coronaviruses can survive for long periods on surfaces and in the air. When an infected person sneezes, coughs, or talks, they can produce infectious respiratory droplets and aerosols. Since droplets are larger, they land on surfaces more quickly.

On the other hand, since aerosols are smaller and lighter, they hand in the air for long periods, which explains why the transmission of SARS-CoV-2 is more likely when the air is drier, and the humidity is lower.

What the study is about

The researchers aimed to determine how temperature affects SARS-CoV-2 transmission, specifically looking at humidity.

The study, which was published in the journal Transboundary and Emerging Diseases, the team has found the number of locally acquired cases of SARS-CoV-2 in Sydney increased as the air became drier and the humidity level dropped.

To arrive at the study findings, the team monitored the daily numbers of reported SARS-CoV-2 cases from New South Wales (NSW) Health. The team also noted that since the cases were reported by postcode, it was easier to identify the source of each one, allowing the team to compile the daily numbers of cases from February to May, matching them to the nearest weather recording stations.

From there, the researchers downloaded meteorological data and utilized the time-series analysis method to project cases based on weather recorded up to 14 days prior.

The team found that they needed only the relative humidity to predict cases of SARS-CoV-2, which is a measure of the water vapor in the air. When there is lower humidity, the air is drier. They discovered that for every 1 percent decrease in relative humidity, there was a 7 to 8-percent increase in cases.

The lockdown between the study period was a substantial contributor in containing the pandemic in the area. Still, the researchers found the same link between dry air and cases, whether or not a lockdown was in force.

However, the team did not see any link between SARS-CoV-2 cases and rainfall, temperature, or wind speed.

Adding to previous findings


Previous studies have also tied humidity and SARS-CoV-2 transmission. For instance, the research team cited a study conducted in China, wherein they found that both drier air and lower temperatures were associated with more SARS-CoV-2 cases.

In May, the research team conducted a study in Sydney, focusing on the early stages of the outbreak. However, in the study, the team did not analyze the findings by area.

“The fact we were able to identify relative humidity as an important factor in both the Chinese winter and Australian summer, using the same research methods, gave us confidence this is a real phenomenon. Our latest study strengthens this hypothesis even further,” Michael Ward, Chair of Veterinary Public Health and Food Safety, University of Sydney and study co-author, explained.

“Of course, laboratory research on SARS-CoV-2, the coronavirus that causes COVID-19, is still in its infancy. But there has been research on closely related coronaviruses, including those that cause sudden acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS),” he added.
curncman
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Aerosolized Transmission

Post by curncman »

Trader, thanks for bringing this to the light. what else is going to be found out in future.. we have to wait and see....One thing we know for sure in future TSOI products will be used in saving many COVID-19 patients from critical conditions and cure all mild covid19 patients from COVID-19
trader32176
Posts: 3538
Joined: Fri Jun 26, 2020 5:22 am

Aerosolized Transmission

Post by trader32176 »

curncman ,

you're welcome !

I thought these 2 studies almost contradicted themselves :o
After reading them both again , I decided they belong together for now .
trader32176
Posts: 3538
Joined: Fri Jun 26, 2020 5:22 am

Aerosolized Transmission

Post by trader32176 »

Public restrooms are dangerous places during COVID-19 pandemic

8/19/20

https://www.news-medical.net/news/20200 ... demic.aspx

Think you don't need to worry about COVID-19 while using a public restroom? A group of researchers from Yangzhou University in China recently reported that flushing public restroom toilets can release clouds of virus-laden aerosols for you to potentially inhale.

If that's not cringeworthy enough, after running additional computer simulations, they've concluded that flushing urinals does likewise. In Physics of Fluids, from AIP Publishing, the group shares its work simulating and tracking virus-laden particle movements when urinals are flushed.

The researchers' work clearly shows public restrooms can be dangerous places for potentially becoming infected from a virus, especially during the COVID-19 pandemic. Other work has shown that both feces- and urine-based virus transmission is possible.

To do this, we used a method of computational fluid dynamics to model the particle movement that occurs with the act of flushing. The specific models are the volume of fluids model and discrete phase model."

-Xiangdong Liu, Researcher, American Institute of Physics

Flushing a urinal, much like flushing a toilet, involves an interaction between gas and liquid interfaces. The result of the flushing causes a large spread of aerosol particles to be released from the urinal, which the researchers simulated and tracked.

What the simulations revealed is disturbing. The trajectory of the tiny particles ejected by flushing a urinal "manifests an external spread type, with more than 57% of the particles traveling away from the urinal," said Liu.

But that's not all. When men use urinals within a public restroom, these tiny particles can reach their thigh within 5.5 seconds when compared to the toilet flush, which takes 35 seconds to reach slightly higher. Particles from urinals, however, "show a more violent climbing tendency," Liu said. "The climbing speed is much faster than toilet flushing."

Urinals are used more frequently within densely populated areas, and the researchers point out that particles will travel faster and farther, which poses a serious public health challenge.

This work underscores how important it is to wear a mask within public places but especially restrooms.

"From our work, it can be inferred that urinal flushing indeed promotes the spread of bacteria and viruses," says Liu. "Wearing a mask should be mandatory within public restrooms during the pandemic, and anti-diffusion improvements are urgently needed to prevent the spread of COVID-19."
curncman
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Joined: Fri Jun 26, 2020 8:27 am

Aerosolized Transmission

Post by curncman »

Trader, scary observation about another way in which COVID-19 can spread through public restrooms and URINALS...all public places are at risk of COVID-19 propagation...Airports, Schools, Universities, Sports Stadiums...I wish COVID-19 dies down soon with any of the TSOI's STEMVACS, JADI CELL and of QUADRAMUNE products.
trader32176
Posts: 3538
Joined: Fri Jun 26, 2020 5:22 am

Aerosolized Transmission

Post by trader32176 »

curncman,
It is scary to think how virus droplets in the air can become launched / aerosolized in different ways .
Usually , we only think about people sneezing and coughing .
trader32176
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Joined: Fri Jun 26, 2020 5:22 am

Aerosolized Transmission

Post by trader32176 »

Researchers compare COVID-19 transmission risk when singing, speaking and breathing

8/21/20

https://www.news-medical.net/news/20200 ... thing.aspx

One of the vastly impacted by the coronavirus disease (COVID-19) pandemic is the world of performing arts. Many concerts, plays, and Broadway shows were canceled due to the fear that singing in an enclosed space might pose a risk for the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Previous guidelines and research have revealed singing has been identified as a potentially “dangerous” activity following the incidence of COVID-19 case clusters in several choirs across the globe. However, there is no clear evidence that the cases were tied to singing or playing brass or woodwind instruments, which were banned in many countries.

Now, a new study* set to determine if singing and playing of woodwind and brass instruments produce more respiratory droplets and aerosols than speaking. Further, they want to know if the size and temperature of the venue will make a difference in the accumulation of aerosol droplets in the air.

Aerosol transmission of COVID-19

The World Health Organization (WHO) has recently acknowledged that SARS-CoV-2, the virus that causes COVID-19 disease, can spread via aerosols suspended in the air when infected people cough, sneeze, or talk.

In a report in May, the U.S. Centers for Disease Control and Prevention (CDC), the health agency said that singing could be considered a superspreading event involving SARS-CoV-2. In the study, after a 2.5-hour choir practice attended by 61 people, including one symptomatic index patient, 32 confirmed and 20 probable secondary COVID-19 cases were reported. From these, three patients had to be hospitalized, and two had succumbed to the infection. The report also showed that the transmission of the virus was likely facilitated by proximity, which is within the 6-feet range, during practice, and exacerbated by singing.

From there, the CDC has recommended avoiding gathering in large groups, including shows, rehearsals, and public events.

In another preliminary research in July, a team of researchers has found that singers, including those who play brass and wind instruments, produce respiratory aerosols at high rates. Put simply, they generate a lot of droplets in the air when they sing or blow.

Another study in early August, funded and supported by the National Federation of State High School Associations (NFHS) and a group of more than 124 performing arts organizations, supported the preliminary results. The second phase of the study explored aerosol from additional singers and instruments, as well as theater performers.

The results of the second phase of the study highlight the importance of masks, distance, time, airflow, and hygiene to create the safest possible environment for bringing performing arts back into rehearsal spaces, performance halls, classrooms, and band rooms.

No riskier than speaking

In the current study, called the PERFORM (ParticulatE Respiratory Matter to InForm Guidance for the Safe Distancing of PerfOrmeRs in a COVID-19 PandeMic) and conducted by experts at the Imperial College London, the researchers carried out several experiments to determine if airborne droplets are produced via breathing, speaking, singing, and playing of brass and woodwind instruments. The research is published on the preprint server ChemRxiv*.

The participants in the study sang and spoke between the decibel (dB) ranges of 50 to 60, 70 to 80, and 90 to 100.

The team has found that singing does not produce substantially more respiratory particles than speaking at a similar volume. The amount of aerosols produced depends on how loud a person is, which could have implications for live indoor performances.

To reduce the risk of coronavirus spread, the researchers recommended singing softly, offering a ray of hope for musicians who were greatly affected by the pandemic since they were restricted from performing in public.

To arrive at the findings of the study, the team recruited 25 professional singers to breathe, talk, cough, and sing into funnels where the small aerosols suspended in the air were measured. The singers performed the activities in an orthopedic operating theater, which is ideal for the experiment because it does not have background aerosols.

The team has found that the lowest volume singing and speaking produced a similar mass of aerosols as breathing. They concluded that singing softly can reduce the risk of COVID-19 transmission.

“Our research has provided a rigorous scientific basis for Covid-19 recommendations for arts venues to operate safely, for both the performers and audience, by ensuring that spaces are appropriately ventilated to reduce the risk of airborne transmission,” Jonathan Reid, a Professor of Physical Chemistry at the University of Bristol, said in a statement.
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TimGDixon
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Aerosolized Transmission

Post by TimGDixon »

Thanks for all the great posts trader - i may not respond to every one of them but for sure i read them.
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