• P.K. Peterson

Preventing COVID-19: Should You Wear a Facemask?

“As coronavirus spreads, facemasks become a ‘symbol of protection’—and a lightning rod for fear”

Naomi Xu Elegant Fortune January 31, 2020

Only one form of contagion travels faster than a virus. And that's fear.

Dan Brown

As of Monday, March 1, at least 63 people were being treated for COVID-19 in the U.S., most of whom were evacuees from Asia. But the origin of at least four cases on the Westcoast that were impossible for doctors to trace, prompted a warning from the Center for Disease Control and Prevention (CDC) that this is the beginning of "community spread." So far, evidence of community spread is most apparent in California, Oregon, and the state of Washington, where the first six deaths due to COVID-19, four in a nursing facility, were recently reported.

Thus it is behooves all Americans to pay attention to authoritative organizations, like the CDC, regarding protection against infection by the causative agent, SARS-CoV-2. This Germ Gem post deals with one such measure—the wearing of facemasks.

If you’ve watched any news channels carrying stories on the COVID-19 epidemic since it started in Wuhan, China in December, 2019, you’ve probably seen crowds of Chinese people all wearing facemasks. You might even have seen a grueling arrest of a mask-less, lawbreaking Chinese citizen who was spotted by a surveillance camera or drone. And as the epidemic spread outside China, mask-wearing Japanese, South Koreans, Iranians, and most recently Italians were portrayed in the news. Given these observations you’ve perhaps concluded that facemasks must be protective, and it may even be time to buy one as the supply is quickly dwindling.

Should you wear a facemask? For now, the answer to the question of whether you should wear a facemask in public is: “No.” But this answer needs to be qualified somewhat because it isn’t yet entirely clear how SARS-CoV-2 is transmitted. (Airborne transmission of virus particles, or droplets containing the virus, by coughing or sneezing seems most likely, but contaminated hands may also do the job.) And the fact of the matter is there are no clinical trials to support or debunk the wearing of facemasks by the public. (I suspect we won’t be seeing such trials anytime soon, considering the challenges of designing and carrying them out.)

The answer “No” also needs to be nuanced a bit because it depends upon your profession. If you’re a healthcare worker taking care of a patient with known or suspected COVID-19, the answer is: “By all means wear a facemask,” just as it would be if you were caring for someone with another highly contagious infection, such as Ebola, Middle East Respiratory Syndrome (MERS), or active pulmonary tuberculosis. But if you aren’t involved in direct care or contact of such infected patients, the answer is an unqualified “No.”

What kinds of facemasks are available. There are two kinds of facemasks to choose from: surgical masks—they protect the environment, including those in it like surgical patients, from the wearer, and respirators, such as N95—they’re tighter fitting and better protect the wearer from inhaling infectious agents. Respirators are certified by the CDC and the National Institute for Occupational Safety and Health.

Size matters. When I was in Beijing a few years ago, I wore an N95 respirator facemask. At that time China, and Beijing in particular, led the world in air pollution. (India subsequently captured the “honor.”) Air pollution is the world’s biggest environmental health problem, and tiny particulates called PM2.5 are a major cause of diseases associated with air pollution.

The prefix N denotes non-oil, meaning that the masks filter out non-oil-based particles. The N95 and N99 masks are supposed to block 95% and 99% of PM2.5 – particulate matter of 2.5 micrometers or less in diameter (about 30 times lesser than the width of a human-hair strand). Coronavirus virions (or 'particles') are spherical particles with diameters of approximately 125 nm (0.125 microns). The smallest particles are 0.06 microns, and the largest are 0.14 microns. This means coronavirus particles are smaller than PM2.5 particles, but bigger than some dust particles and gases.

What does the CDC say? The CDC does not recommend the routine use of respirators outside of workplace settings (i.e., in the community). Instead, the CDC recommends everyday actions to prevent the spread of respiratory viruses, such as avoiding people who are sick, avoiding touching your eyes or nose, covering your cough or sneeze with a tissue, and washing your hands frequently. People who are sick should stay home and not go into crowded public places or visit people in hospitals.

Not everyone is able to wear a respirator due to medical conditions that may be made worse when breathing through a respirator. Before using a respirator or getting fit-tested, workers must have a medical evaluation to make sure that they are able to wear a respirator safely.

Achieving an adequate seal to the face is essential. U.S. regulations require that workers undergo an annual fit test and conduct a user seal check each time the respirator is used. Workers must pass a fit test to confirm a proper seal before using a respirator in the workplace.

Unlike NIOSH-approved N95 respirators, surgical facemasks are loose-fitting and provide only barrier protection against droplets, including large respiratory particles. No fit testing or seal check is necessary with these facemasks. Most facemasks do not effectively filter small particles from the air and do not prevent leakage around the edge of the mask when the user inhales.

The role of surgical facemasks is for patient source control, to prevent contamination of the surrounding area when a person coughs or sneezes. Patients with confirmed or suspected COVID-19 should wear a facemask until they are isolated in a hospital or at home. The patient does not need to wear a facemask while isolated.

Prioritizing N95 respirators. Currently, surgical masks are flying off the shelves throughout many countries in Asia. And N95 respirators, which are considerably more expensive, can be purchased online. While members of the general public don’t need to purchase either type of facemask, N95 respirators clearly are required for healthcare providers caring for patients with COVID-2019.

If necessary, governments need to assure their availability. It would also be valuable to launch a campaign advising against public use of facemasks because they are of no proved value and foster the spread of fear. (Speaking of governments, ironically at about the same time that COVID-19 emerged leading to mandated wearing of facemasks in Wuhan and Shanghai, a law banning the wearing of facemasks by dissidents in Hong Kong was declared unconstitutional.)

Su Hu Image 3_edited.jpg

Main Page images courtesy of Shuxian Hu, MD. Dr. Hu is a scientist in the Neuroimmunology Research Laboratory at the University of Minnesota.


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© 2020 by Phillip K. Peterson
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