[Skybird]

Some good and some not so good news form the german Max Planck Institute.



A new study shows that you can infect yourself by aerosols of an infected in short time and at distances of even 3m.Well, I always never beleived that those propagated 1.5m do the trick, it just does not make sense.


But then, well-fitting FFP2 masks can push the risk into the low per-mill-range of probabilies.



They also say that FFP2 masks protect up to 75 times better than those thin surgical masks. Why am I not surprised (and do not use the latter)...?

Even three meters away does not protect. Even at this distance, it takes less than five minutes for an unvaccinated person standing in the breath of a corona-infected person to become infected with almost 100 percent certainty. This is the bad news. The good thing is: if both are wearing well-fitting medical or even better FFP2 masks, the risk drops dramatically. In a comprehensive study, a team from the Max Planck Institute for Dynamics and Self-Organization in Göttingen investigated how well which masks protect and when they are worn. The researchers determined the maximum risk of infection for numerous situations and took into account a number of factors that have not previously been included in similar studies.

The Göttingen team was also surprised at how great the risk of infection with the coronavirus is. "We would not have thought that at a distance of several meters it would go so quickly until you absorb the infectious dose from the breath of a virus carrier," says Eberhard Bodenschatz, Director at the Max Planck Institute for Dynamics and Self-Organization. Because at this distance the air you breathe has already spread conically in the room; the infectious particles are diluted accordingly. The particularly large and therefore particularly virus-rich particles also fall to the ground after a short distance through the air. “Nevertheless, in our study we found an enormous risk of infection even at a distance of three meters if you meet infected people with a high viral load, as occurs with the predominant delta variant of the Sars-CoV-2 virus, for a few minutes and doesn't wear a mask, ”says Eberhard Bodenschatz. And such encounters are unavoidable in schools, restaurants, clubs or even outdoors.
Well-fitting FFP2 masks reduce the risk to at least the per mil range

As high as the risk of infection is without a mouth and nose protection, medical or FFP2 masks are effective. The Göttingen study confirms that FFP2 or KN95 masks are particularly effective at filtering infectious particles from the air we breathe - especially when they close as tightly as possible at the edges. If both the infected and the non-infected person wear well-fitting FFP2 masks, the maximum risk of infection after 20 minutes is barely more than one per thousand, even at the shortest possible distance. If their masks are badly fitted, the likelihood of infection increases to around four percent. If both of them wear well-fitted surgical masks, the virus will be transmitted within 20 minutes with a maximum of ten percent probability. The investigation also confirms the intuitive assumption that for effective protection against infection, the infected person in particular should wear a mask that filters as well as possible and tightly fits.

The contagion probabilities determined by the Max Planck team each indicate the upper limit of the risk. "In everyday life, the actual probability of infection is certainly 10 to 100 times smaller," says Eberhard Bodenschatz. Because the air that flows out of the mask at the edges is diluted so that you do not get all of the unfiltered air you breathe. We accepted that, however, because we cannot measure how much breathing air someone wearing a mask reaches another person in all situations, and because we wanted to calculate the risk as conservatively as possible, ”explains Bodenschatz. "If even the greatest theoretical risk is small under these conditions, you are on the safe side under real conditions." For the comparison value without the protection of a mask, however, the safety buffer is significantly smaller. “For such a situation, we can determine the virus dose that an unprotected person inhales with fewer assumptions,” says Gholamhossein Bagheri, who as a research group leader at the Max Planck Institute for Dynamics and Self-Organization played a key role in the current study.

When calculating the risk of infection, the Göttingen team took into account a number of factors that have not yet been included in comparable estimates. The researchers have investigated how a bad fit of the mask weakens the protection and how this can be prevented. "The membranes of FFP2 or KN95 masks, but also of some medical masks, filter extremely effectively," says Gholamhossein Bagheri. "The risk of infection is then dominated by the air that flows in and out at the edges of the mask." This occurs when the edge of the mask is not close to the face. In extensive tests, Bagheri, Bodenschatz and their team measured the size and quantity of breathing particles flowing past the edges of masks that fit differently. "A mask can be perfectly adapted to the shape of the face if you bend its metal bracket into a rounded W before putting it on," says Eberhard Bodenschatz. "Then the contagious aerosol particles can no longer get past the mask and glasses no longer fog up."

The team also considered that droplets that people spread when they breathe or speak dry out in the air and become lighter. As a result, they stay in the air longer, but have a higher virus concentration compared to the droplets immediately after they emerged. When you breathe in, the opposite happens: the particles absorb water again, grow like a drop in a cloud and therefore more easily get stuck in the airways.

Even if the detailed analysis by the Max Planck researchers in Göttingen shows that tightly fitting FFP2 masks protect 75 times better than well-fitting surgical masks and that the way a mask is worn makes a clear difference: even medical masks significantly reduce the risk of infection Compared to a situation without any mouth and nose protection. "That is why it is so important that people in the pandemic wear a mask," says Gholamhossein Bagheri. And Eberhard Bodenschatz adds: "Our results show once again that wearing a mask in schools and in general is a good idea."



https://www.ds.mpg.de/3822295/211202...und_infections