New, potentially more contagious strains of COVID-19 are spreading in the U.S. and around the world. And suddenly you’re hearing that everyone should be wearing “better masks.” Or two masks at a time. When it comes covering your mouth and nose, is it time to kick things up a notch?
“Maybe,” says Medical Director Cecilia Stuopis.
But, she cautions, the perfect should not be the enemy of the good. “I’d hate to see someone stop wearing a mask because they think that the one they happen to have isn’t good enough,” she says. “Our many months of experience here at MIT have demonstrated that when most people wear face coverings most of the time, we can be highly successful at preventing transmission of the virus. We’ve had a few cases of person-to-person transmission in our community, primarily during unmasked interactions or gatherings that included eating and drinking. But, with a couple of exceptions, we have not seen any viral transmission between individuals who were wearing face coverings of any type.”
While cloth masks vary greatly, there’s more than anecdotal evidence that they work. A scientific brief from the CDC, published in November, summarizes a number of epidemiological studies illustrating the effectiveness of cloth face masks in preventing viral spread. For example, a study done last spring compared the daily growth in new COVID-19 cases before and after mask mandates were implemented in 15 states and the District of Columbia. Results showed that new cases declined by an average of 0.9 percent after five days and by 2 percent after three weeks, leading researchers to conclude that the implementation of these mandates likely prevented more than 200,000 cases of COVID-19 by the third week in May. As to why masks work? Look no further than the work of MIT’s own Isolat team. By their calculations, between 50 and 100 percent of the reduction in R0 (the average number of people infected by one infectious individual) achieved through extreme social distancing measures last spring could have been attained through the adoption of cheap cotton masks alone, if worn by everyone in the population.
But when might you need something more than that spiffy cloth mask your Aunt Mildred sewed for you? Those exceptions that Stuopis mentioned — where transmission happened despite both individuals wearing masks — may offer some hints. “Those cases all involved individuals who, although masked, were unable to distance adequately and were working in small, poorly ventilated spaces for extended periods of time due to the nature of the work itself,” Stuopis explains. “Think, for example, electrical or telecom work, or other types of maintenance activities that require more than one person for safety reasons and need to be carried out in a crawl space.”
You may not find yourself sharing a crawl space anytime soon, but you can rank your own daily activities by transmission risk — and remember that any activity involving other people will become somewhat riskier as more contagious variants become more common. Taking a lunchtime walk outdoors? Wear a cloth mask, but don’t sweat the thread count. Spending an extended period of time indoors with other people outside of your household, especially if the ventilation isn’t great or distancing isn’t always possible? Think about stepping up your mask game.
Do I need an N95?
An N95 mask, or an “N95 particulate-filtering facepiece respirator,” is a medical-grade respirator that is designed to fit tightly around the nose and mouth. When worn correctly, it forms a tight seal on the wearer’s face and blocks out at least 95 percent of small airborne particles, according to the CDC. While some public health experts have argued that everyone in the country should be wearing an N95, they are relatively hard to find and can be expensive. Counterfeits abound, and the CDC continues to request that this type of personal protective equipment, or PPE, be reserved for frontline healthcare workers who are at the highest risk of repeated exposure to the virus.
And in most situations, an N95 would be overkill and impractical, Stuopis says. “Speaking from personal experience, I can tell you that if you’ve been properly wearing a correctly fitted N95, it will leave marks and even bruises on your face when you take it off.” she notes. “A properly fitted N95 is very uncomfortable. And an improperly fitted N95 isn’t as effective.”
Then what are the best alternatives?
For higher-risk situations, some experts are recommending a KF94, the certified mask used in South Korea. It’s readily available online and relatively inexpensive — about $40 for a pack of 20. It’s made of a nonwoven material, similar to that of the N95, but has ear loops instead of bands that go around the back of the head, so it won’t fit as snugly. It’s disposable but safe to reuse a few times.
But there are other ways to achieve close to the same filtration results. A recent study tested 10 different types of face coverings for their effectiveness at protecting both the wearer and others. Based on those results and the results of similar studies, the authors recommend two different “maximal protection” options:
- A three-layer mask with outer layers consisting of a flexible, tightly woven fabric that can conform well to the face and a middle layer consisting of a non-woven high-efficiency filter material such as vacuum-bag material, or
- A cloth mask tightly on top of a surgical mask where the surgical mask acts as a filter, and the cloth mask provides an additional layer of filtration while improving the fit.
If these masks fit well, the authors say, they should provide an overall filtering efficiency of greater than 90 percent for particles 1 μm and larger, the size of respiratory aerosols considered most important in transmission of the virus.
What about double masking?
“If you have a physical covering with one layer, you put another layer on, it just makes common sense that it likely would be more effective,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, on the Today show last month. But the combination recommended above — a surgical mask covered by a cloth mask — gives you the best combination of filtering and comfort. “Wearing two multi-layer cloth masks might be protective,” Stuopis says, “but breathing would be tough.”
Surgical masks, which are readily available to MIT DLCs (departments, labs, and centers) through the online MIT COVID-19 store, have good filtering efficiency but tend to gape open at the sides. Add a well-fitting cloth mask on top — especially one that ties around the back of your head instead of attaching with ear loops — and you get a snugger fit overall with less leakage. This will make both masks perform better than either would on their own.
How do I know if my mask fits well enough?
Wondering how much fit matters? Just take a look at this video! To see if your mask (or mask combo) makes the cut, you can perform a modified form of the “user seal check” to test for leakage: Put your hands over the mask, and exhale gently. You shouldn’t feel air coming out the side or up toward your eyes. Then inhale sharply. You should feel the face-piece collapse slightly under the negative pressure. You also want to move your head in different directions to see if the mask stays in place. Read a paragraph or two of text — this article would work — to make sure it doesn’t slide around too much when you talk. And, glasses wearers, if your specs are fogging up, your mask fit is not up to snuff.
If the fit of your face covering is found wanting, a recent study showed that several “hacks” improved both fit and filtration. These included tying the mask’s ear loops and tucking in side pleats, fastening ear loops behind the head with a claw-type hair clip, or adding a band of nylon hosiery. Another option is a mask brace or mask fitter, which can be purchased inexpensively or fabricated from open-source plans.
Protect others; protect yourself.
While it’s important to wear the best possible mask for the situation, a well-fitting mask of any type protects both other people and yourself, Stuopis emphasizes. “The new viral variants have us thinking more about mask quality,” she says, “but it’s still the same virus, and the same precautions that have worked so far will continue to slow the spread. Vigilance is key. Now more than ever.”
It’s been a long year, and we’re all tired. But now is not the time to become complacent or so overly fixated on one type of precaution, like masking, that we let our guard down in other areas. “We know what works,” Stuopis says. “We just need to keep doing it.”
