Mon. Sep 26th, 2022
Colorful face masks are piled on a table.
enlarge Self-sewn protective face masks in a fabric shop on April 3, 2020 in Jena, Germany.

As COVID-19 cases surge across the country, some health experts are now recommending that apparently healthy members of the public wear cloth masks when out and about. On April 3, President Trump announced a new federal recommendation calling on the public to wear cloth masks to prevent people who are infected but have no symptoms from unknowingly spreading the disease.

The recommendation is a reversal of previous guidelines on the use of masks. So far, officials from the World Health Organization, the U.S. Centers for Disease Control and Prevention, and other agencies around the world have discouraged the public from wearing masks unless they are sick or caring for someone who is sick. They noted that there is little evidence to support mass masking and that the limited data we have suggest it may only marginally reduce disease transmission at best.

With evidence that benefits are scarce, experts have also raised concerns about potential harm. Wearing a mask can give people a false sense of security, some experts said. This can lead some members of the public to be lax about other much more critical precautions, such as keeping two meters away from others, limiting trips and washing their hands frequently and thoroughly.

In addition, wearing an uncomfortable, clunky mask can cause some people to touch their faces more, some argued. Any touch to the face has the potential to transfer virus particles from contaminated hands to entry points, such as the eyes, nose and mouth. And even if a mask wearer’s hands are clean to begin with, touching the mask can contaminate their hands if there are virus particles on the outside. If so, a mask wearer could then inadvertently transfer virus particles from their mask to their face, negating any benefit of having the mask. They can also transfer the virus from their mask to their environment by touching surfaces, where the virus particles can be picked up by other people.

Finally, they argued that the masks that would be most effective in stopping the novel coronavirus — SARS-CoV-2 — are things like N95 respirators and surgical masks, which are in short supply worldwide. These should no doubt be saved for the heroic frontline health workers, who risk their lives every day to treat patients with COVID-19 during this overwhelming pandemic.

While experts are unanimous on that last point — that good medical masks should go to health professionals first — the other points are now up for debate.

With SARS-CoV-2 now spreading widely and unchecked through communities across the country, experts are looking more favorably at the limited data behind masks that prevent the spread of disease to the public. In a recent commentary in The Lancet, a group of British and Hong Kong researchers argue that “there is an essential distinction between absence of evidence and evidence of absence.” And while there are no large, high-quality studies on the use of public masks, there is some data to support the use of masks.

As for the potential harm from wearing masks, such as a loaded face and wearers easing other precautions, experts are now dismissing the concerns. Wearing a mask in public can keep people alert to current health risks in public, some experts say. A conspicuous mask strapped to your head is a constant reminder to be aware of potential viral transmission. And – as a bonus – if everyone wears a mask, it can reduce the likelihood of stigma from those who wear it because they are sick.

Of course, wearing a mask doesn’t replace other interventions, such as staying six feet apart or practicing good hand hygiene, says Joseph Allen, an expert in exposure assessment science in the Department of Environmental Health at Harvard T.H. Chan School of Public Health. “It’s just an extra layer of protection.”

“The scale and scope of what we’re dealing with requires or obliges us to take every possible precaution,” he says.

As such, some experts – Dr. All Inclusive – are now in favor of the healthy public wearing homemade cotton masks or other face coverings that can serve as a basic physical barrier.

“It’s not that good [as medical masks]but it’s better than nothing,” said Dr. all.

So with the contradictory reasoning and logic, what does the data on masks actually show? How were they rejected before, but now embraced? Here is an overview of relevant data.

Transfer

First, to understand why masks can be helpful in blocking SARS-CoV-2 transmission, it’s important to understand how the coronavirus is transmitted. And frankly, we still don’t know all the answers to this question.

So far, SARS-CoV-2 appears to mainly pass from one human to another by being launched in relatively large respiratory droplets. These are released when an infected person breathes, talks, coughs or sneezes. These droplets are relatively heavy, they generally travel not much more than two meters from their launch site, and they follow a ballistic trajectory, that is, they fall to the ground after the detonation. But if they land on a person’s face before or fall on a surface that a person will quickly touch, they can cause another infection.

There is also the possibility that SARS-CoV-2 can spread in smaller respiratory droplets called aerosols (less than 5 micrometers). These are droplets that we exhale that are so small that they can remain suspended in the air for minutes to hours. Experts at WHO and elsewhere say the data so far suggests that aerosol transfer is not the primary way the virus spreads, although it is still possible. So far, aerosol transmission appears to be a primary concern for health professionals while performing certain medical procedures on COVID-19 patients, such as placing a tube in their airways to facilitate breathing (intubation). This allows the virus to spread airborne in hospital rooms and linger in the air.

Whether SARS-CoV-2 is nebulized in the everyday environment is still unknown and is under debate. Some experts, such as Dr. All, believe it could happen. Others are more skeptical of the idea, as infected people infect only two to three other people on average. If every COVID-19 patient created contagious clouds of SARS-CoV-2 everywhere, some experts would expect the patients to infect many more people on average. For example, measles has been associated with airborne transmission for decades, and each measles patient can infect an average of 12 to 18 people — or more. There is even evidence that the measles virus can spread through ventilation systems.

While that doesn’t seem to be the case for SARS-CoV-2, experts like Allen warn that the size of virus-containing respiratory droplets is a continuum, not subject to obvious limitations or strict rules. There is some evidence that if SARS-CoV-2 gets into aerosols, the virus can survive for hours in the air under laboratory conditions.

Finally, there is some evidence that SARS-CoV-2 particles that land on surfaces or objects can hang out and potentially be picked up by others. These contaminated surfaces and objects that can then transmit the infectious virus particles are called fomites. Masks can prevent a wearer from placing a fomite-infected hand on the face, but masks can also act as fomites.

By akfire1

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