Wear a Mask. No, Don’t Wear a Mask. Wait: Yes, Wear a Mask.

When it comes to whether everyday citizens like you and me should cover our faces, experts are divided. Here’s why — and what to actually do.

Photo: Noam Galai/Getty Images

The only thing moving faster than the novel coronavirus, it seems, is the guidance on who should be wearing face masks.

On February 29, which was somehow only a little over a month ago, the US Surgeon General Jerome Adams, MD, MPH, tweeted:

Despite the Centers for Disease Control and Prevention estimating (in 2006!) that in the event of a severe influenza pandemic, at least 1.5 billion medical masks would be needed by the healthcare sector and an additional 1.1 billion would be needed by the public [emphasis mine], the US was now facing a severe shortage: In early March, the Department of Health and Human Services (DHHS) estimated that US healthcare workers would need 3.5 billion respirator masks to fight a full-blown coronavirus pandemic over the next year, only 1 percent of which was available in DHHS’s Strategic National Stockpile (the department has since ordered 500 million more after initial attempts were undercut).

In response to the shortage, the CDC issued new guidance, stating that if face masks were unavailable, healthcare professionals “might use homemade masks (e.g., bandana, scarf) for care of patients with Covid-19 as a last resort” — ideally in combination with a face shield, as the efficacy of cloth masks against the coronavirus is unknown.

Since then, Americans — and businesses like New Balance, GIR, and Orucase — have rolled up their sleeves and started making their own face masks. The majority will be donated to healthcare workers, but everyday citizens are adopting the practice, too: My Instagram feed is full of pictures of people wearing DIY masks, handkerchiefs, and scarves wrapped around their faces, despite the fact that the CDC still advises against wearing one unless you’re sick or caring for someone who is.

For many, it seems logical: Viruses can be expelled or inhaled through the nose and mouth, so putting a barrier in front of both should lower your risk of infection, right? And if not, then why did Hong Kong health officials say universal mask-wearing helped them limit the spread of the coronavirus, and why did Chinese officials make mask-wearing mandatory in certain parts of the country?

Medical experts are starting to ask the same questions. Over the past two weeks, there’s been an explosion of op-eds posted on The Lancet, Medscape, the Center for Infectious Disease Research and Policy, and of course, Twitter, with former FDA commissioner Scott Gottlieb, MD, arguing:

So, what’s the right move here? Should you be scrounging for a box of surgical masks? Sewing your own? Covering your face with a scarf when you’re out in public? There’s no easy answer, but we’ve rounded up the best available evidence so you can make a more informed decision.

Why Health Experts are Divided

Whether face masks are effective at keeping you healthy depends on how a virus is transmitted. The novel coronavirus is a respiratory virus and respiratory viruses are generally spread via droplets (think: an infected person sneezes on you) or direct contact (an infected person sneezes into their hand and then touches a doorknob. You touch the doorknob, contaminating your fingers, and then touch your face).

The problem is, droplets aren’t the only airborne particles that can carry a virus — they’re just the biggest. Coughing, sneezing — even just exhaling — can also generate tiny, lighter particles, known as aerosols.

Guidance from the World Health Organization (WHO) and the CDC has stressed that the novel coronavirus is spread primarily through droplets and contact — not aerosols — which is why they recommend six feet of social distancing and regular hand-washing.

But, writes Lisa Brosseau, ScD, a national expert on respiratory protection and infectious diseases, “the exact modes of transmission for SARS-CoV-2 — the technical name of the virus that causes Covid-19 — are unknown. To date there is no direct research-based evidence describing exactly how SARS-CoV-2 is transmitted.”

Brosseau and others argue that the WHO and the CDC are basing their recommendations on an oversimplified and outdated dichotomy that classifies infected fluid as “droplets” or “aerosol” and doesn’t take into account the real-life way pathogens travel through the air. And that’s a problem, because aerosol-based viruses are believed to be more “airborne.”

“We’ve all seen the picture of a person coughing and there’s a cloud of aerosol that comes out,” says Margaret Sietsema, PhD, an assistant professor of environmental and occupational health sciences at the University of Illinois at Chicago and a director of the International Society for Respiratory Protection. “But not every one of those aerosols that come out that person’s mouth is the same size. Some of the particles are going to be larger and some of the particles are going to be much smaller. We know that small particles stay airborne much longer, so it’s not totally unlikely that the smaller particles are going to travel further, and someone else will be able to breathe them in at some distance.”

“If someone makes a journey they would not otherwise make, or puts themselves into a riskier situation (infection-wise) because of perceived security from wearing a mask, then masks are more a problem than a solution.”

Including at distances beyond six feet. But whether pathogens travel that far depends on a ton of factors, including humidity levels and wind speeds. Early, non-peer-reviewed studies have found novel coronavirus aerosols may linger in healthcare settings. And while the mere presence of airborne particles doesn’t mean the pathogens are strong enough to spread infection, when you consider additional research suggesting these aerosols can stay viable in the air for up to 3 hours and the estimate that individuals with mild or no symptoms may be causing up to 79 percent of document cases of Covid-19, it is worrisome.

Still, says Sietsema, “I wouldn’t be too concerned that there are aerosols everywhere. And that’s because when we go outside, we have a natural ventilation system. We have wind and weather that kind of diffuses particles pretty quickly.”

Two Types of Face Masks That Work

Another reason experts are divided? The limited science supporting the use of supply-constrained face masks. According to the best available research, there are two types of masks most likely to protect you from contracting the coronavirus or passing it on to others.

N95 respirator masks are designed to protect the wearer from their environment. In the US, they must meet Occupational Safety and Health Administration (OSHA) fit test protocols. When worn properly, they form an airtight seal over the user’s nose and mouth, blocking at least 95 percent of tiny (as small as 0.3 micron) airborne particles, like those expelled during aerosol-generating procedures such as intubation. They’re meant to be used once, and then disposed of.

An early, non-peer-reviewed study out of Wuhan, China supports N95 respirator use. Researchers found that despite having a 733 percent higher exposure rate to the novel coronavirus, none of the 278 medical professionals who wore N95 respirators and disinfected and cleaned their hands frequently developed Covid-19. Comparatively, 10 of the 213 healthcare workers who wore no mask and disinfected and cleaned their hands occasionally did develop the disease.

Surgical masks, aka procedural masks, fit more loosely and help block large-particle droplets, splashes, sprays, or splatter from spreading. They’re made of something called melt-blown fabric. “We’re talking about fibers where one filament has a diameter of less than one micron, so we are in the nano area,” Markus Müller, the sales director at German company Reicofil, a major provider of melt-blown machine lines, told NPR. Like N95 respirators, surgical masks are also designed to be single-use.

Among people with the flu, surgical masks can decrease the exhalation of large viral droplets 25-fold, according to a 2013 study. And in households with sick children, healthy caretakers who faithfully wore surgical masks were 60 to 80 percent less likely to catch the influenza-like illness.

In fact, although laboratory studies show that surgical masks are inferior to N95 respirators in protecting people from the flu, a 2020 systematic review and meta-analysis published by the Chinese Cochrane Review found no statistically significant differences between the two in real-world usage. That may be because N95 respirators may cause more discomfort, the study authors reason, which can lead to lower compliance with best practices.

And when a separate 2011 Cochrane review evaluated how effective multiple physical interventions (screening at entry ports, isolation, quarantine, social distancing, barriers, personal protection, and hand hygiene) were at interrupting or reducing the spread of respiratory viruses, the researchers determined that wearing a surgical mask or a N95 respirator is the measure with the most consistent and comprehensive supportive evidence.

So N95 respirator and surgical masks both appear to be helpful in preventing the spread of respiratory viruses — great! Unfortunately, they’re in short supply and need to be saved for the healthcare workers on the front lines of fighting Covid-19. That leaves the rest of us with one potentially viable option: cloth masks.

“Viruses can’t enter through the skin, so a mask literally provides a barrier to stop us from helping them get in by touching our mouths and noses.”

What’s the Deal with Cloth Face Masks?

Cloth face masks typically consist of one or more layers of fabric. They fit like a surgical mask and are primarily used to prevent the spread of infection from the wearer. These are the masks armies of volunteers have mobilized to create for healthcare professionals.

Proponents of cloth masks often reference a small 2013 study that found that both surgical masks and homemade masks reduced the total number of microorganisms expelled when coughing. However, the homemade mask was about one third as effective at filtering the type of small pathogens consistent with influenza.

“A homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals,” cautions lead study author Anna Davies, BSc, now a research facilitator in the Department of Veterinary Medicine at the University of Cambridge. “It would not be protective against aerosols.”

In fact, the research was just a “proof of principle study” conducted to determine if an intervention is worth studying further, says Davies, who was a public health microbiologist at Public Health England at the time of the study. “If the results had shown equivalence with surgical masks (or better), or no efficacy, there would have been clear policy implications and further research. Because the results were somewhere in between (probably better than nothing but not great), it never went any further.”

Unfortunately, the best available evidence we have on cloth masks — a 2015 randomized controlled trial — produced even more discouraging results. Not only did cloth masks prove to have extremely poor filtration (3 percent efficiency compared to 56 percent for surgical masks), but the healthcare workers who wore them experienced significantly higher rates of viral infection compared to those who wore surgical masks. It’s unclear why.

“Cloth masks rated poorly in our study, but perhaps this was because people did not wash the cloth masks well enough, or that the particular fabric was poor quality,” writes lead study author Raina MacIntyre, PhD, an infectious disease and personal protective equipment expert at the University of New South Wales in Australia.

One of the criticisms of cloth masks is that they can collect moisture, becoming a breeding ground for bacteria. Others argue that wearing a mask may make people more likely to touch their face more. Or that masks could confer a false sense of security.

“Pandemics require us to change our behavior — our socialization, hygiene, work and more — collectively, and knowing our fellow citizens are on board is important for all efforts.”

“If someone makes a journey they would not otherwise make, or puts themselves into a riskier situation (infection-wise) because of perceived security from wearing a mask, then masks are more a problem than a solution,” says Davies.

But there are lots of potential benefits, too. Most notably, they can be a reminder not to touch your face. “Viruses can’t enter through the skin, so a mask literally provides a barrier to stop us from helping them get in by touching our mouths and noses,” says Davies.

And, as techno-sociologist Zeynep Tufekci points out in The New York Times, when we wear a mask, we show our fellow citizens we’re taking the situation seriously. “Masks are an important signal that it’s not business as usual as well as an act of solidarity. Pandemics require us to change our behavior — our socialization, hygiene, work and more — collectively, and knowing our fellow citizens are on board is important for all efforts.”

In an ideal world, everyone with Covid-19 would have access to a surgical mask, but that’s not the reality we’re living in. Instead, research suggests that thousands of asymptomatic people may be walking around spreading the disease during a rapidly progressing global pandemic. When faced with the decision between wearing a cloth face mask that promises negligible results or doing nothing at all, it’s hard to argue against the former.

Even MacIntyre — the author of the 2015 trial that found cloth masks may increase infection — has told healthcare workers, “If there is nothing else, of course you should use whatever (mask) you can get or make your own. The physical barrier may afford some protection.”

Davies feels the same way: “Homemade masks sit at the lower end of the ‘protection’ scale, but will probably lower risk if handled correctly in combination with isolation of infected individuals, social distancing, hand hygiene, etc.” Plus, using a cloth mask will help preserve surgical masks for health professionals.

As for WHO, they still maintain that cloth (e.g. cotton or gauze) masks are not recommended under any circumstance. But the CDC may be yielding to the building pressure.

According to a federal official who spoke to the Washington Post on the condition of anonymity, CDC officials are considering altering the official guidance to encourage people to take measures to cover their faces amid the coronavirus pandemic.

Cloth Mask Best Practices

If you decide to make your own face mask, there are no shortage of tutorials online — Davies recently published the template and instructions she gave to volunteers in her study, and this one from the Hong Kong Consumer Council doesn’t even require fabric or a sewing machine — but know that a CDC-approved version doesn’t exist. Given the shaky evidence surrounding DIY options, you’ll want to optimize everything from the materials you use to how you handle the mask (more on that below).

Prior studies on cloth masks have shown that three factors are important: the closeness of the weave, the number of layers, and the type of cloth. In general, you want to use a comfortable fabric with a tight weave that won’t restrict your breathing. “Layered fabric may be a better choice,” writes MacIntyre, “but again, we lack evidence.”

In her 2013 homemade mask study, Davies and her team evaluated a variety of materials that people were likely to have on hand and found that the slightly stretchy quality of 100-percent cotton t-shirt fabric offered the best mix of fit and performance. Pillowcases also rated highly.

Regardless of what materials you use, keep the following guidelines in mind:

  • Wash your hands before putting on or taking off your mask and at regular intervals throughout the day — wearing a mask doesn’t excuse you from practicing smart personal hygiene.
  • “Always wear your face mask in the same orientation,” says Davies. The same side should always face outward. Using two different colors or patterns to make your mask can help with this; or just mark one side with ink.
  • Remove the mask when eating; do not just pull it down onto your chin.
  • When taking off your mask, grasp the ties or elastics — not the front of the mask — to reduce the risk of contaminating your fingers.
  • If you’re using a reusable cloth mask, wash it after each use or, at the very least, place it in a paper bag to dry out, recommends the CDC. “I suggest that people forced to use cloth masks have at least two and cycle them, so that each one can be washed and dried after daily use,” writes MacIntyre.

And, last but not least, continue practicing social distancing. “Everyone needs to reduce their exposure [to the coronavirus] as much as possible,” says Sietsema. “And that means staying home.”

Former magazine editor and current freelance reporter who spends way too much time on PubMed. Let’s hang out: @dkos07. (she/her)