Cobb County has reinstituted its mask mandate for Cobb government buildings as the highly transmissible Omicron variant of COVID-19 spreads through the community.

The Cobb courts have their own protocols in place, and the Cobb County School District has chosen not to follow the CDC’s best practices for the protection of students and staff.

But most reputable sources of health care information recommend masking as part of the effort to reduce the transmission of COVID-19, along with vaccination and social distancing.

During earlier variants in the first wave of the pandemic, the CDC recommended that the public not purchase N95 masks because of the shortage of Personal Protective Equipment (PPE) for health care professionals, but they’ve changed that recommendation now that the supply of PPE has caught up with the demand.

But the following questions often arise: What type of mask should I wear? How long can I wear them? Can they be cleaned?

SciLine, a service whose goal is “to help get more science into news stories,” recently asked a group of scientists for guidance on masking.

SciLine first asked the scientists “With the omicron variant circulating, what type of mask best prevents transmission of COVID-19?”

“With the omicron strain circulating, we need today to use high-grade masks. This could be N95s or FFP2s in other parts of the world. It’s no longer just about the source control, so protection, mitigation of what comes out, but it’s also protection of the person wearing the mask for what is being inhaled.”

• Lydia Bourouiba, Ph.D.
  Associate professor of civil and environmental engineering, Massachusetts Institute of Technology

“So that would be the KN95 or the N95 masks. They filter out 95% of particles that are out there. With omicron it’s a much more transmissible virus, so it either transmits more efficiently because people are shedding much more virus into the air or because it’s able to—fewer particles are needed to be able to infect you. So if you’re standing next to somebody who is infected, it’s going to take a lot longer for that to transmit to somebody if you’re wearing an N95 mask.”

• Deborah Fuller, Ph.D.
  Professor of microbiology, University of Washington School of Medicine

“Before COVID was on the scene, people have done work for 25 years in HIV on how to get people to be the most protected. And what we know from all that work is that it’s a combination of how well the intervention works and how adherent you are to it. So an N95 mask offers the best protection, but only if you’re going to be highly adherent, wear it correctly, and wear it consistently.”

• Dave O’Connor, Ph.D.
  University of Wisconsin Medical Foundation professor of pathology and laboratory medicine, University of Wisconsin-Madison

“As far as what type of mask best prevents the transmission of COVID-19, I don’t think the answer has changed really significantly over the course of the pandemic. Honestly, the best mask to wear is the best one that you can get your hands on, and right now I think that a KN95 represents that for most of the general public. They’re fairly readily available and not too expensive. The only thing better than that—that most people could get their hands on—would be an N95, and those are generally professionally fit for medical professionals or other people who need respiratory protection at work. And so, without the advantage of professional fit, a KN95 still offers the best protection for the general public.”

• Joshua L. Santarpia, Ph.D.
  Associate professor of pathology and microbiology, University of Nebraska Medical Center; science and technology advisor for the National Strategic Research Institute

The next question was “If the best masks are not available, what are the next best options?”

“When the highest-grade masks are not available, one should absolutely avoid crowded spaces and, particularly, poor ventilation. High ventilation is still very important. But also, one should be wearing, still, a mask that has multiple layers—for example a surgical mask with multiple layers or cotton with multiple layers—but the key is the seal around the nose and the mouth. If we have good materials but lack of seal, the air will go through all the openings on the side. So both are important.”

• Bourouiba
  

“So the next best option would be to wear a surgical mask with a cloth mask over it. I’ve seen people do a lot of that. That actually—sort of doubling up masks gets a little bit closer with the N95.”

• Fuller
  

“So a surgical mask is a minimum standard that you should be wearing when you’re out and around other people. Cloth masks might be a bit more stylish, but they’re a lot less consistent in terms of their construction and quality. So it’s better to wear a surgical-grade mask or better whenever you’re going to be around others.”

• O’Connor
  

“If you can’t find a KN95 or something that represents sort of the best protection that you can find, surgical masks offer the sort of the next—would be sort of the next step down. Cloth masks are really at the bottom end of the spectrum for most people. Primarily because it’s hard to evaluate the efficacy of a cloth mask; it’s so variable; there are no standards. So it’s really difficult to say whether cloth masks of any type are really working for you or not. But if you lean towards surgical masks or better, at least you have some idea of the amount of protection that you’re getting.”

• Santarpia
  

How long is it safe to reuse N95 masks? Can they be cleaned?

“If one has to reuse their N95s or high-grade masks, it’s possible to do so. But it depends on the level of exposure that the mask has received. In other words, one can reuse a mask—for example for a week, if the mask is used just for an hour or so per day in a very low-contamination space where no known cases of COVID were present, for example. If one is in a very highly contaminated situation, with known cases, crowded space, for an entire day, then the mask shouldn’t be reused.

“In terms of decontamination, it’s possible to do it, but it varies. There are no foolproof methods. But essentially, exposure to the sun, if we have the ability to do so, is a possibility. Other methods that involve decontaminant are likely to fail because they would actually degrade the mask much faster. So there are no foolproof methods. UV light has been used in hospitals in some cases. It’s not foolproof, as well, but it can provide some level of decrease of contamination.”

• Bourouiba
  

“In my experience, N95 masks typically have the straps break within a couple of weeks. But maybe that’s because I’m unusually hard on mine. I think it’s entirely reasonable to reuse them for a week or two or until they become uncomfortable or show signs of excessive visible wear.”

• O’Connor, Ph.D.

“So in terms of the length of time you can use an N95 mask and how well and whether or not you can clean it, I would say that you can reuse them probably for several days under light wear conditions, where you’re sort of intermittently wearing it off and on and you’re setting it aside when you’re not wearing it. In terms of cleaning for reuse, I generally prefer—because things are much more available, N95s, KN95s, are much more available than they once were—that people just discard them if they feel they’re dirty. If you’ve been around someone who’s sick, or if you’ve had to wear it for long periods of time, it’s better just to discard it and get a new mask than to try to clean it.”

• Santarpia

SciLine then asked: What else should people know about masking while the omicron variant circulates?

“The combination really of being vaccinated and wearing a mask is going to be your best defense against omicron. We have to remember that even when you’re vaccinated you can potentially get a breakthrough infection. And if you have a breakthrough infection, even if you are healthy and you’re not feeling any symptoms, it’s quite possible that you could be shedding virus. And so we think of masks as really a two-way street. A lot of times we think we wear masks to protect ourselves, but wearing a mask is also to protect others. So even if you’re vaccinated, you’re not feeling symptoms, you’re feeling pretty confident that you’re not going to get it, when you go out in public it’s important to still wear that mask, especially where you’re going to be in crowded areas, because there is always a possibility you have a breakthrough infection. And if you do, you can transmit that to somebody else who could get seriously ill.”

• Fuller
  

“The most important thing to know about masking is that it is something that you can do today to minimize your risk of becoming infected with the virus, or if you happen to be infected, of giving it to other people. And so one of my friends has made the analogy that it’s like fencing around a racetrack. That if you have a chain-link fence, you’re not going to be as well protected from debris coming off a race car as you will if there’s a concrete barrier. But that means you just might want to stand a little bit further back. So there’s different ways that you can use masks as barriers to protect yourself from the virus. But again, it’s this combination of what protects the best multiplied by what you’re going to be most adherent to.”

• O’Connor

“In terms of how we should change our masking during omicron, I think there’s enough evidence to suggest that the infectious dose is likely to be lower, and that people are likely producing more infectious virus, to suggest that we need to invest in higher efficiency filtration for ourselves and for our own protection. The higher efficiency your mask, the more time you have between when you first interact with someone and when you eventually get the disease. So it just buys yourself more time and lowers your likelihood of acquiring the disease.”

• Santarpia

About SciLine

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