Which protective masks protect, and which even more transmit infection with Covid-19


The United States already has a record five million infected with the new coronavirus, and all efforts to stop the spread of the infection have failed. Although there is pressure for consistent and widespread vaccine testing and development, experts say continued wearing of masks will bring the pandemic under control within “a few weeks”.

A new study published in Science Advances addresses which masks are most effective and which do not help but do harm in the fight against the Covid-19 pandemic.

The analysis, conducted by researchers at Duke University School of Medicine, relies on an “optimal measurement method” that uses a laser beam and a camera to track the number of drops emitted by masked people.

Of the 14 masks, two that proved to be the least effective were masks made from a scarf tied around the face and so-called neck warmers.

The safest mask is N95, which reduces droplet transfer below 0.1 percent.

Handmade masks made of cotton and polypropylene, some of which are made of material as well as an apron, have also been shown to be effective, with drop transfer ranging from 0.1 to 0.4 percent.

The knitted mask missed a large number of drops, from 0.1 to 0.6 percent.

But no mask missed as many drops as a scarf tied or wrapped around the neck and mouth and from the neck and the so-called. neck and face heaters, and which are actually more dangerous than having no mask at all (110 percent drops leak, even 10 percent more than when a person is without a mask).

How is it possible?

Researchers explain how these masks can actually spread more viruses than a person who does not wear a mask at all.

“We noticed that someone talking through the mask (especially those tied scarves and ‘heaters’) seemed to disperse the largest droplets into much smaller droplets… which explains the apparent increase in the number of droplets compared to other masks,” they wrote. These small drops can be extremely dangerous in terms of transmission.

“Because smaller particles stay in the air longer than larger ones (larger ones fall faster), using such a mask can be counterproductive,” they say.

Dr Amesh Adalja, a scientist at Johns Hopkins Health Center, said the study was important, especially in the United States, where there are large numbers of people who oppose wearing masks.

“People do not really understand that not all protective masks are the same and there are some that will be more or less effective. “And I think when you make those decisions, you need to know things like this.”

Given the speed of transferring drops from the scarf or neck heaters, he points out that such things should not be used at all.

“Not every mask is the same… I think a lot of people wear these things to cover their face just to fill out a form, not realizing that they need to be effective to serve a purpose.”

For those who still do not know why masks are necessary, the doctor says that asymptomatic spread is one of the most important factors in the pandemic.

“There are a lot of people who do not know they are infected, and covering the face is one of the ways to keep people safe. “If everyone knew if they were being treated or not, that would be a different story, but the fact is that most do not know if they are infected or not.”

More testing could potentially reduce the need for masks, says Dr. Adalja. But until then, they are vital to starting a pandemic.

“If we have quick tests that we can know in a minute after we leave the house whether we are infected or not, that would be a whole other thing, but we are far from that.” “So this is the measure we have left,” said Dr. Adalja.


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