Apr 28, 2021
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Indoor social distance has little effect on SARS-Cov-2 risk

For the study, the results of which are published in the journal PNAS, MIT specialists developed a formula for assessing the risk of infection in an enclosed space, taking into account various factors – the number of people, the duration of contact, activity, wearing masks, the quality of ventilation, adherence to social distance.

Calculations have shown that in the calm interaction of several people – for example, at a small meeting – during conversations, a small amount of aerosols containing the virus is released, which will quickly settle on the floor. However, if there are many people in the room talking, screaming or singing loudly, droplets with viral particles can stay in the air longer.

So, if 25 people are in the same room wearing masks (and of course, they change them regularly) and talk, then if an infected person joins them, those present can be exposed to the virus in two days. However, if the same 25 people do not wear masks and do not talk, and the infected person is in the same room with them, the time interval during which infection can occur is reduced to 77 minutes. If all these people do not wear masks and sing (for example, at a small concert), this period is reduced to 3 minutes. At the same time, it does not matter at all whether they observe social distance in all cases.

The time interval during which infection can occur is sharply reduced if the infected person is a carrier of the “British” variant of the B.1.1.7 virus, which is known to be highly contagious. However, the likelihood of the spread of the pathogen is reduced if ventilation systems with high-quality filters are used in the room.

The study authors also noted that children are much less susceptible to infection. For example, in a restaurant with good ventilation, 25 children can safely be without masks in the same room with the carrier of the original variant of the virus for up to four hours, with carrier B.1.1.7 for up to two hours.

“Our study indicates that the six-foot rule is inadequate (approx .: 1.8 meters) and offers a more rational alternative to reduce the risk of coronavirus transmission,” the scientists said, noting that wearing masks and using good indoor ventilation is a more effective measure for protection against SARS-Cov-2.

Previously, similar conclusions were made by scientists at the University of Central Florida, who created a computer model of a university audience with students and teachers, and then reproduced the air flow and calculated the possible risk of spreading SARS-Cov-2.

The results confirmed the benefits of masks as they prevent direct exposure to viral aerosols by creating a gentle flow of warm air.

The study also showed high ventilation efficiency with a good air filter, which reduces the risk of contamination by 40-50% compared to non-ventilated rooms. It creates a constant air flow that directs aerosols into the filter, preventing them from concentrating in the room. At the same time, scientists have confirmed the recent recommendations of the US Centers for Disease Control (CDC) to reduce social distance from six to three feet (91 cm) while wearing masks.

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