Researchers used human models to show how respiratory clouds and possible coronaviruses can spread in different situations.

New research shows that a social distance of 9.8 feet (3 meters) is not enough to ensure protection from Covid-19. Even at that distance, an unvaccinated person can be infected with almost 100% certainty in less than 5 minutes while standing in the breath of a Covid-19 patient.

This is bad news.

The good news is that if two people are wearing well-fitting medical masks, or better yet N95 or FFP2 masks, the risk is greatly reduced.

Researchers have investigated the degree of protection under which masks are worn. In the process, the researchers determined the maximum risk of infection in a variety of situations and considered several factors that were not included in similar studies. This comprehensive study was published in the Proceedings of the National Academy of Sciences (PNAS) on December 7.

The team from the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany, includes Eberhard Bodenschatz, adjunct professor of Aerospace and Mechanical Engineering at the School of Physics and Engineering, School of Arts and Sciences, on the spread of coronavirus.

Bodenschatz, director of the Max Planck Institute, said: "We would not have imagined that within a few meters, the breath of a virus carrier would take such a short time to absorb the infectious dose."

At that distance, the researchers found that the exhaled air had spread in the air in a cone; the infectious particles were diluted accordingly. In addition, very large and virus-rich particles will fall to the ground after passing a short distance in the air.

"In our research, we found that if the viral load of the infected person is very high, and if the viral load of the infected person is high, the risk of infection without a mask is very high after a few minutes, even at a height of three meters. Within distance-2 viruses," Bodenschatz said. Such encounters are inevitable in schools, restaurants, clubs and even outdoors.

Nevertheless, medical or FFP2 masks can still effectively protect. The study confirmed that FFP2 or N95 masks are particularly effective at filtering infectious particles in the air—especially if the mask is sealed as tightly as possible on the face. If both infected and non-infected people wear fitted FFP2 masks, the maximum risk of infection after 20 minutes is almost no more than one in a thousand, even at the shortest distance. If their masks do not fit, the probability of infection will increase to about 4%. If both parties wear well-fitting medical masks, the virus is likely to spread within 20 minutes, with a maximum probability of 10%. The study also confirmed an intuitive hypothesis that in order to effectively prevent infection, the infected person should especially wear a mask that filters as much as possible and fits closely to the face.

The probability of infection determined by the Max Planck team indicates the upper limit of risk in each case. In daily life, the actual probability of infection must be 10 to 100 times smaller. "This is because the air flowing from the edge of the mask is diluted, so you won't get all the unfiltered breathing air," Bodenschatz said. "But the reason we make this assumption is because we cannot measure how much air a person wearing a mask breathes to reach another person under all circumstances, and because we want to calculate the risk as conservatively as possible.

"Under these conditions, even if the biggest theoretical risk is small, then under actual conditions you are on the safe side."

However, for comparison values ​​without mask protection, the safety buffer zone is much smaller. "In this case, we can use fewer assumptions to determine the dose of virus inhaled by unprotected people," said Gholamhossein Bagheri, head of the research team at the Max Planck Institute and lead author of the study.

When calculating the risk of infection, the researchers considered many factors that were not previously included in comparable studies, including how inappropriate masks weaken protection and how to prevent this from happening.

“FFP2 or KN95 mask materials, as well as some medical mask materials, have a very good filtering effect,” Bagheri said. "Then the risk of infection depends on the air coming out and in from the edge of the mask." This happens when the edge of the mask is far away from the face.

In a well-designed experiment, Bagheri, Bodenschatz and their team measured the size and number of breathing particles flowing across the edges of different masks.

Bodenschatz said: “If you bend its metal band into a round W before putting on the mask, it can adapt to the shape of the face very well.” “Then infectious aerosol particles no longer pass through the mask—nor the glasses. Fog again."

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