Advice and explanation of COVID-19 face mask

It is a seemingly simple question that separates the country from experts since the outbreak of COVID-19. Do non-sick civilians need to use a mask to limit the spread of the disease?

Center for Disease Control and Prevention for several months Maintained The only thing that needed to be worn was a sick person or someone who handled it. This concept comes from the idea that basic medical masks provide little help to protect the wearer, but instead primarily prevent sick people from squirting infectious droplets through their nose and mouth. You. In addition, frontline healthcare professionals needed to prioritize limited supplies. who Agree.

However, some countries used a different approach, Suggest And even Request The use of masks in certain cases when people were outside the house. Many scientists also I started Suggests that a broader mask policy might be a good idea.

Then a few days later Speculation, President Donald Trump Announced On April 3, the CDC Recommend The fact that people are using cloth surface coverings in crowded places, he said he did not follow, despite his emphasis on being spontaneous.

“If you use a mask, it will actually be spontaneous,” he said. “You can do it. You don’t have to do it. I choose not to do it.”

Authorities quoted new data that the “ significant part ” of people infected with the new coronavirus could spread the virus to others even if they had no symptoms. Revision That Recommendation“Whenever people have to go to public places,” says people should wear a cloth surface cover.

“The cloth surface cover is not intended to protect the wearer, but may prevent the spread of the virus from the wearer to others.” Updated CDC website Read. “This is especially important if someone is infected but has no symptoms.”

The United States is moving toward a more approachable approach, but some experts have reserved this policy. Cloth masks have not been well studied and there is little real evidence to recommend medical masks to the general public. These guidelines can also exacerbate the lack of medical masks and flashbacks if people don’t wear the covers properly or fall into a false sense of security.

At the same time, other scientists have pointed out lab studies showing that wider adoption of masks may still be useful, even with less effective do-it-yourself models. The widespread use of masks also keeps people from touching the face and signals the severity of the pandemic.

Review some of the research and thinking behind the face mask and explain why the opinions are divided. But first, it is important to recognize that, despite the discussion, most experts agree on the most important issues:

• If there is a benefit to having a healthy person wear a mask, the effect may be small. No one should think that you are protected with a face mask. It is important that people are 6 feet away and keep their hands washed. As the CDC says, cloth coversNot a substituteRepresents social distance.
• Healthcare professionals should prioritize medical masks and ideally use N95 masks when treating people with COVID-19.

The role of the mask

Depending on the design, masks can limit the spread of infection from infected people Source controlAnd / or protect the wearer from infection.

For COVID-19, transmission Virus transmission is thought to occur primarily through respiratory droplets, and if the infected person coughs or sneezes, it can adhere to the mouth and nose of another person. Droplets can also contaminate surfaces that are touched before others touch the face.

Here, a basic surgical mask (a spacious disposable mask) can help. When a sick person wears a mask, infectious droplets can become trapped in the mask. Doctors and nurses wearing such masks are also likely to cough and sneeze and may be somewhat protected.

However, researchers also suspect that the new coronavirus, SARS-CoV-2, remains in the air as very small droplets called aerosols, which can be inhaled by nearby people. Ah Investigation Released on March 17 New England Medical Journal Aerosol transmission is called “plausible”; in experiments, the virus was “viable” for up to 3 hours in a machine-generated aerosol, but half of the particles did not become infected after about an hour . TThe role of this mechanism in the spread of the virus is not yet clear. Unlikely This allows the virus to travel long distances, but scientists Increasingly confident That it can happen to some extent.

“I think it’s likely that all transmission routes are involved here,” said occupational health professor. Margaret Shietema According to the University of Illinois at Chicago, “The best line of defense is the ventilator because this disease can be inhaled.”

Often cited in ventilators N95 maskIs a close-fitting disposable mask that creates a seal on the face and has a special filter that captures at least 95% of the airborne particles that pass through. (To avoid confusion, we will no longer use the mask as a mask.)

In contrast to N95, surgical masks are not intended to provide protection against aerosols. As CDC blog Surgical masks are “ designed to provide barrier protection against droplets, but are not regulated for particulate filtration efficiency and form a reliable seal on the wearer’s face that is reliable for respiratory protection. No. “

Limited evidence, diverse views

Recently the cinema, Judging Evidence about the University of Minnesota Infectious Disease Research Center mask suggests N95 ventilators for healthcare professionals interacting with COVID-19 patients, but there is sufficient evidence to support a broader masking policy, including healthy people I do not believe there is.

Masks may be able to reduce infection by catching larger droplets that erupt, but it is only applied if the person is symptomatic, and those with symptoms should stay in public spaces anyway Claim not.

“I don’t think the transmittance will drop before the mask becomes a symptom, because the air doesn’t choose a more resistive path (through the mask). It just bypasses the mask,” she says. Said.

She also expressed concerns that mask recommendations could reduce social distance and could complicate efforts to protect surgical masks for first-line healthcare professionals. did.

But other scientists disagree, saying that masks are not completely effective, but are likely to be better than nothing.

Benjamin cowling, Epidemiologists at the University of Hong Kong do not buy the idea that surgical masks are useless to the general public.

“Indeed, they could believe that they would / better / work well when used by healthcare professionals, especially when used in combination with other protective equipment and actions,” he said. Is from a healthcare professional mentioned in the email, but it is useless if worn by others. “

Immediately after release Investigation Co-authored by Cowling Natural medicineResearchers have found that surgical masks reduce the amount of respiratory virus exhaled when breathing or coughing on specialized machinery.

Previously, Another study Using a similar setting, Cowling et al. Found that surgical masks reduced the amount of influenza RNA that researchers could detect from both small and large respiratory droplets. The effect was much stronger with larger droplets, but this study shows that the mask can reduce aerosol to a limited extent.

Although these types of studies suggest that surgical masks can theoretically limit the spread of respiratory viruses, they are still a step away from showing that masks are effective public health measures in the general population I am.

After all, practically a mask Can be harmful If people give up social distance, they will eventually touch their face or always touch the outside of a potentially contaminated mask.

Even those who support the use of wider public masks have acknowledged the lack of direct evidence of this type. so Lancet Respiratory Medicine Commentary article Proposing to use facemasks more “rationally” to combat COVID-19, the authors described available evidence as “rare.”

Some studies have evaluated various face masks in hospitals and other healthcare contexts, but few studies have tested whether face masks are effective in the community and whether face masks that exist are inconsistent , No significant impact was seen.

For example, Cowling told us the best evidence from randomized controlled trials, Systematic review Of 10 studies that tested face masks for their ability to limit the spread of flu in homes and dormitories. While many trials have struggled to get people to actually wear a mask, suggesting that increased compliance may have an impact, but reviews suggest that “ using face masks Nor did the flu transmission drop significantly, and many of the trials were too small to draw firm conclusions.

“Based on a summary of randomized controlled trials, there may be some, but not so significant, effects.” Elaine Shufon, A statistician and epidemiologist at Oxford University, Lancet Respiratory Medicine Commentary in the interview.

Still, she thought it was wise for the country to start considering face masks. “Insufficient evidence does not mean that the intervention itself is ineffective,” Feng said. “And in this situation, I think the best way is to rely on all available non-pharmaceutical interventions.”

Cloth and DIY mask

Few studies have been done on fabric masks compared to surgical masks and respirators.

2015, Researcher It was published First randomized controlled trial of cloth masks shows that Vietnamese hospital workers are 13 times more likely to get a flu-like illness when wearing cloth masks than disposable surgical masks .

Because the cloth mask group had a higher incidence of respiratory infections than the control group, they sometimes wore surgical masks according to standard hospital practices. However, because no group did not wear the mask at all, researchers could not tell if the cloth mask still provided some protection to the wearer.

“[T]“ He found a much higher infection rate with cross-mask arms, ” the authors write, “ may be interpreted as harm caused by cross-masks, the effectiveness of medical masks, or a combination of both. there is.”

Several other studies have examined how well certain fabrics or designs work in laboratories that block the transmission of droplets and particles. However, the author of the trial in Vietnam paper None of these masks has been tested in clinical trials to address their relevance to COVID-19.

2013 Investigation Testing a household-use mask showed that the cotton T-shirt seemed to have the ability to remove bacteria and viruses, but the mask was not much more effective than a surgical mask. The group concluded that homemade masks are better than no masks, but “should only be considered as a last resort.”

Stricter 2010 testResearchers at the National Institute of Occupational Safety and Health attacked T-shirts, towels, sweatshirts, and scarves with nanoparticles and evaluated the filtration capacity of DIY mask fabrics. Although the performance of the materials was a pale color compared to the N95 ventilator, the authors noted that they provide “ only marginal respiratory protection ”, but most fabrics have at least some particles Was caught.

Lindsay MaA professor of engineering at Virginia Tech, studying viral infections, warned that people should not rely on homemade masks to prevent inhalation of the virus in the air, but for those seeking a unique design With some practical tips.

“ The material needs to be thick and densely woven, like kitchen towels and thick T-shirts, and the mask needs to fit snugly around the nose and mouth without gaps, ” she emailed. .

National Academy of Sciences explain In a 2006 report on the potential for the use of improvised face masks during a pandemic, tighter fabric constructions may make filtration work better, but there are some trade-offs. “[A]As the tightness of the structure increases, respiratory resistance increases, thereby affecting the user’s comfort when using the device, ” said the report, which states, “It may affect use. There is. “

If you put on a mask

For those who have chosen to wear a mask, Feng Shui has recommended learning appropriate techniques to reduce accidental infections from the mask itself. As demonstrated by WHO videoIt is important that you do not touch the outside of the mask, and if you do, wash your hands.

CDC also Offer Advice and some patterns for those who create their own masks.

But most importantly, the mask does not protect you or exempt you from social distance and hand washing. As Feng Shui said, “you should be at home.”