As the Covid-19 pandemic has unfolded, authorities in different places have said different things about whether healthy people should go around wearing face masks to reduce the spread of the disease. Officials in China, Hong Kong and Taiwan have recommended it in crowded places such as buses or subway cars. A handful of countries in eastern Europe have mandated mask wearing in public. Experts at the World Health Organization have continued to say there’s no such need. Those in the U.S. started out with that position, but in early April recommended people use cloth face coverings when in public rather than medical masks. That’s because the popular demand for masks has aggravated a shortage of them among medical personnel, who need them the most.
Why the different guidance?
Precedent explains part of it. In eastern Asia, the practice of wearing medical masks in public is well-established. It emerged as a convention during the 2002-2003 epidemic of severe acute respiratory syndrome (SARS), which also was caused by a coronavirus. For another thing, there’s no scientific consensus on the value of wearing a mask in public. A few small studies have suggested that widespread use of face masks by the public may have reduced transmission in outbreaks of influenza and SARS, which like Covid-19 are respiratory diseases. However, the evidence is not generally considered conclusive.
Why not wear one out of caution?
Many medical specialists say one should, especially in light of evidence that a significant portion of those infected with the novel coronavirus don’t show symptoms and so may remain out and about. Others have argued that it’s irresponsible for members of the public to buy up masks that are in short supply. In its new guidance, the U.S. Centers for Disease Control and Prevention said, “Do NOT use a facemask meant for a healthcare worker.” The scarcity among health-care providers, U.S. Surgeon General Jerome Adams has said, raises the overall risk to the community: Infected providers can spread the virus to the uninfected and once sick can’t look after patients. The argument is that everyone is better off if medical masks are reserved for those who certainly require them and who can’t avoid exposure to people who are infected or might be.
What about non-medical masks?
As long as medical masks remain in short supply, some health specialists, including those at the CDC, are proposing that people cover their faces with home-made masks. They can be hand-sewn from fabric or improvised using a bandana or scarf, for instance.
How can masks help?
The evidence so far is that the novel coronavirus spreads in respiratory droplets — spatters of liquid expelled when an infected person coughs, sneezes or even speaks. These droplets are usually heavy enough to fall immediately to the ground or surrounding surfaces. Transmission can occur if the droplets reach the mouth, nose or eye of someone nearby, either directly or from an unwashed hand that’s touched a contaminated object or surface. When an infected person wears a face cover, the droplets can be caught by the mask rather than being expelled. In theory, wearing a face covering could also help protect people who are uninfected, if it stops them from touching their face. However, according to the WHO, there is currently “no evidence” that public mask wearing by healthy people prevents infection with respiratory viruses such as the one that causes Covid-19.
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What’s the guidance for health-care workers?
Protocols prescribe that patients infected with the virus that causes Covid-19 should be isolated and given a mask to wear. This will usually be the type worn by surgeons — the loose-fitting, one-size-fits-all kind that’s rectangular when flat. Health-care providers who deal with such patients or with confirmed cases are directed to wear a more sophisticated mask called a respirator, which is designed to protect the user.
How are respirators different?
They come in different sizes so they can be fit to the wearer’s face to provide a tight seal. That forces the user to pull air through the device’s filter rather than through gaps on the sides. They are designed to keep out not only respiratory droplets but also smaller aerosolized particles that can carry infectious agents and float for a time through the air. Airborne transmission has not been reported for Covid-19, but there is a risk that certain medical procedures, such as tracheotomy and airway suction, can generate virally contaminated aerosols. Respirators are uncomfortable to wear for a long period of time. They retain heat and exert pressure on the face, and some people find they make it difficult to breathe, which can make them unsuitable for those with cardiac and respiratory conditions.
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How are professionals dealing with the shortages?
The CDC issued guidance on how to conserve limited gear and what to do if it runs short. The measures, which don’t meet usual standards, include using respirators beyond their designated shelf life and wearing the same one to attend to several patients without removing it. The agency said that limited reuse of respirators might become necessary but counseled caution. It said a last resort would be to turn to untested versions, including homemade masks. Some U.S. hospitals have already adopted these options, with several recruiting the public to sew masks.
Are there downsides to wearing a mask?
In guidance issued April 6, the WHO said the use of masks by healthy members of the public may create a false sense of security, leading people to neglect essential measures such as hand-washing and keeping at a distance from other people. It also said wearing a mask can encourage people to touch their faces, which can increase the chances of becoming infected with the coronavirus. Health care professionals emphasize that if you’re going to use a mask, it’s vital to do so correctly or you could become infected through contact with it: put it on with clean hands, replace it as soon as it becomes damp, remove it from behind without touching the front, wash your hands afterward, and dispose of the mask properly. The WHO counsels against reusing masks that are made for a single use.
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