Tighten up your face mask or double it up. That’s the latest advice from the U.S. Centers for Disease Control and Prevention as dangerous new strains of the novel coronavirus spread across the United States and health officials scramble to get vaccines in arms.
Wearing a washable cloth mask on top of a disposable medical-style one— “double-masking”—can double the level of protection against the fine airborne droplets that carry the SARS-CoV-2 pathogen, a team led by John Brooks, chief medical officer for the CDC’s COVID-19 emergency response, concluded in a study the agency released on Wednesday.
The CDC’s recommendation is a clear signal—it’s time to consider doubling down on masks. It’s the one proven way to fight the pandemic while still keeping the economy open to some degree and awaiting more vaccine.
ADVERTISEMENT
Experts predict it could be summer before there are enough shots for all Americans who want them. And while we wait, we have to contend with at least three major new strains of the virus: B.1.1.7 from the United Kingdom, B.1.351 from South Africa and the Brazilian lineage P.1.
B.1.1.7 reached the U.S. in December and has since spread to around half of states. P.1 and B.1.351 showed up in America last week. There are signs that the new strains are more transmissible on the cellular level than the baseline virus and might also partially resist the immunity-inducing effects of the new vaccines.
Despite this, as many as half of Americans still aren’t wearing a single mask, much less two of them. Health officials face an uphill battle selling the idea of extra protection to millions of people who—even after a year and nearly 470,000 U.S. deaths—can’t be bothered to protect themselves and the people around them at all.
It was clear early on that masks help to limit transmission of the novel coronavirus by blocking the thin aerosol mist that carries the virus from the lungs of an infected person to the lungs of someone else nearby.
“Medical-procedure” N95 and KN95 masks with their fine polypropylene material have been the standard since the start of the pandemic. The CDC estimated these sometimes short-in-supply masks, if properly fitted with a tight seal around the mouth and nose, can filter out 95 percent of airborne particles coming from another person.
But even a simple cloth mask with its coarse material and loose fit offers some protection, filtering out up to half of particles if the thread count is high enough, according to the CDC.
Based on that guidance, 14 states plus Washington, D.C. have maintained mask-mandates, as have hundreds of counties and cities across the United States. Generally speaking, the mandates require people to wear a mask over their mouth and nose while out in public and near other people.
It stands to reason that if one loose mask helps, a tighter one—or two—should help even more.
To test that assumption, Brooks’ team experimented with two uncommon mask-fits: wearing a cloth mask over an N95-style medical-procedure mask (“double-masking”) and knotting the ear loops of an N95 and then tucking in and flattening the extra material close to the face (“knotting and tucking”).
Brooks’ team rigged up pairs of mannequins. One “coughed” and expelled aerosols like a human being. The other “breathed” and inhaled the aerosols. The testers put the mannequins six feet apart in a closed room, had the first mannequin cough, then measured the amount of particles inside the mask of the second mannequin.
They tried it 10 different ways with the three different masks: an N95 by itself, a knotted-and-tucked N95, and a cloth mask on top of an N95. With each mask type, there were three setups. The cougher would wear a mask and the inhaler wouldn’t. The inhaler would wear a mask and the cougher wouldn’t. Then they’d both wear a mask.
The control involved both mannequins wearing no masks, coughing and inhaling freely. In that case, the inhaler sucked in eight micrograms of particles. Strap a loose N95 on the inhaler alone, and it still breathed in 7.5 micrograms of particles. Give the cougher an ill-fitting N95 and the particle load dropped to five micrograms. When both mannequins wore a loose N95, the inhaler caught just 1.5 micrograms.
Knotting and tucking the N95s helped—a lot. When either the cougher or inhaler alone wore a knotted-and-tucked N95, three micrograms worth of particles made it across the room. When Brooks’ team strapped the carefully-fitted medical masks to both mannequins, the inhaler breathed in less than half a microgram.
But double-masking was the gold standard. Layering masks on either mannequin allowed just 1.5 micrograms to spread. Double-masking both the cougher and inhaler matched the half-microgram spread of the knotted-and-tucked N95s.
The CDC team noted several caveats. Most masks are made for adults, so fits on children might be looser—and protections weaker. Beards can interfere with a mask’s fit. Perhaps most importantly, the CDC’s tests “were intended to provide data about their relative performance in a controlled setting,” Brooks and his colleagues wrote.
Still, the data is clear. “The effectiveness of cloth and medical procedure masks can be improved by ensuring that they are well-fitted to the contours of the face to prevent leakage of air around the masks’ edges,” Brooks’ team wrote. For the most protection, get everyone to double-mask.
Good luck enforcing that on a community level, however. “Consistent and correct use of any intervention requires education, training and monitoring,” Jeffrey Klausner, a former UCLA professor of medicine who also worked at the CDC, told The Daily Beast.
Mask mandates are already weakly enforced. Adding layering or folding to the mandates would surely make them even harder to put into practice. “I am not convinced this experiment is scalable in the real world,” Lawrence Gostin, a Georgetown University global health expert, told The Daily Beast.
Despite how widespread mandates are, just half of Americans cop to actually wearing their masks in many situations, according to a January analysis by the Dornsife Center for Economic and Social Research at the University of Southern California.
Fifty-two percent of survey-takers said they wear masks while around people from other households. Of the 14 percent of Americans who had recently gathered in a group of 10 or more, only 46 percent wore a mask.
“The first step—wearing the mask in the first place—is still the most important one,” Keith Jerome, a University of Washington virologist, told The Daily Beast.
But some states and communities are giving up on enforcing even that basic level of mutual protection. Iowa Governor Kim Reynolds, a Republican, lifted all pandemic restrictions—including a mask mandate— on Friday. Ominously, officials detected B.1.1.7 in Iowa for the first time just four days before Reynolds made her call.
There’s no evidence the new strains make masks and other personal protective equipment, or PPE, any less effective at blocking potentially virus-laden aerosols. “PPE works equally,” Klausner stressed.
But the strains’ apparent higher transmissibility means a given amount of the virus could be more likely to cause an infection. That underscores the continuing importance of wearing a mask.
Or better yet, two masks. Just don’t expect local authorities to make you do it.
