Masks: What the Science Says, and What Lies Ahead

November 20, 2020 | 11:53 am
Nik Anderson/Flickr
Taryn MacKinney
Investigative Researcher

Since the COVID-19 pandemic began, health experts have advised the public on the use of masks. Today, the consensus is clear—mask up!—but the whys and hows of mask-wearing have changed over time. Here’s what we know now, and what we must do to stay safe.

How does the novel coronavirus spread?

Any time we breathe, speak, shout, sing, cough, or sneeze, we spray tiny particles from our mouths and noses—great news for the coronavirus that causes COVID-19. The virus can hitch a ride on these particles, which may land in another person’s eyes, mouth, or nose.

Some of these particles, called droplets, are large and heavy enough that they fall to the floor quickly, within six feet or so—a distance we’re all familiar with by now. But other particles are so small and light they can drift through the air, perhaps for hours, filling spaces like cigarette smoke. These are called aerosols, and we expel 1,200 of them for every droplet. More great news for the virus.

But we aren’t powerless to stop its spread. One of the best tools for combatting COVID-19 is also one of the simplest: masks.

How do masks work?

The virus that causes COVID-19 is tiny (25 million could fit in the period at the end of this sentence) but the particles they ride on are larger—often large enough to get caught in a mask’s material. Like a screen door that keeps out biting bugs, a good mask filters droplets and aerosols from the air you breathe, protecting you and others from infection. And although we have much to learn, what we do know paints a convincing portrait of masks’ effectiveness.

Why should you wear a mask?

Are you worried about your parents or grandparents? Your children? How about your own safety? Anxious about your local mom-and-pop stores, hit hard by the pandemic?

If any of these sounds like you (and if you’re human, at least one probably will), wearing a mask is a vital step. One study found that subjects who wore masks in risky situations were 70% less likely to become infected than those who didn’t. Another found that, in households with at least one COVID-19 case, the risk of other family members becoming infected fell by nearly 80% when everyone wore masks. After hospitals in Massachusetts began requiring masks, fewer health care workers became infected.

Another research team estimates that surgical masks and quality cloth masks are 67% effective in protecting the wearer, and if you do catch the virus, masks may even blunt the severity of the disease.

Masking up could help our economy, too. An analysis from Goldman Sachs found that increasing mask-wearing by just 15% could prevent the need for lockdowns that would cost the economy $1 trillion—some 5% of gross domestic product.

How and when should you wear a mask?

If you’re near other people and you have a face, chances are you should wear a mask.

But while any mask is better than no mask, not all masks are created equal. Cloth masks made of two or more layers of tightly-woven material—600-thread-count cotton, for example, or a combination of cotton and silk—are far more effective than masks made of loose, thin, or single-layered fabric, like bandanas. Remember, the particles on which viruses hitchhike are tiny. The thinner the fabric and looser the weave, the more easily a virus can slip through.

No matter the mask, all is for naught if you wear it incorrectly. Gaps around the sides can halve a mask’s filtering effectiveness, and you’re more likely to fiddle with a mask that doesn’t fit. A well-fitted mask should be snug, covering your nose and extending under your chin—a sort of bear-hug for your face. And avoid touching the front of your mask when you’re wearing it. My little cousin, in typical teenage-boy fashion, has a unique way of remembering this: “If you pretend your mask has poop on it,” he insists, “then you won’t touch it.” Whatever works. Finally, make sure to wash your mask. The CDC has guidance on how to do so properly.

Is wearing a mask enough?

Masks are necessary, but they must be used alongside other tools in the public health toolkit.

Social distancing is the most crucial of these tools. Staying more than six feet away from others in public—at the grocery store, pharmacy, or park—is a start. But duration of exposure matters too. The longer you’re near potentially infected people, the greater your risk, especially indoors and without ventilation. This is because the aerosols we exhale may accumulate in the air and travel 20 or 30 feet.

An article in EL PAÍS models this brilliantly. Let’s say six friends gather in a room in a private home. One of them is infected with COVID-19—we’ll call him John Doe. According to the scientific model used by EL PAÍS, after four hours of talking loudly without masks, John infects all five of his friends, regardless of how far apart they sit. If they wear face masks but still talk for four hours, John infects four friends (even with masks, prolonged exposure amplifies risk). But if the group wears masks, stays for two hours instead of four, and ventilates the room by opening windows, John infects only one friend.

Why does the science keep changing?

Since COVID-19 exploded onto the global scene, our knowledge of the disease has grown and, in some cases, spurred confusion. In March, health experts, concerned about limited medical supplies, advised against mask-wearing for healthy people. But in April, as evidence grew that universal masking reduced the spread of the disease, experts reversed this stance. Similarly, experts have long promoted the six-foot-distance rule to prevent infection from virus-laden droplets. But in recent months, as evidence mounts that aerosols can also cause infection, guidance has evolved.

These changes may seem puzzling, but they are par for the course in science. A far cry from Hollywood’s depictions of instantaneous “Eureka!” moments in labs or hospitals, most scientific progress is a slow, incremental accumulation of knowledge over time. Scientists conduct research, check and re-check data, weigh conclusions, and submit their work for scrutiny by peers and journals.

So what’s different now? The messy course of science—normally hidden behind the scenes—has been shoved into the public spotlight. Scientists know that setbacks, errors, and uncertainties are part of the process, but the rest of us, anxiously watching from the sidelines, may not.

This doesn’t mean the science is wrong. Far from being a weakness, science’s strength is its ability to grow, change, and build our collective knowledge about the world. And as scientists learn more, we must continue to listen and adapt.

How high are the stakes?

The nation has reached an unthinkable milestone. As of November 20, more than a quarter of a million people in the United States have died from COVID-19. Many of them died alone, separated from loved ones because of contagion risk. Tens of thousands of these deaths were preventable.

And things could get worse. Without measures like mask-wearing and social distancing, a winter surge could kill another 100,000 to 200,000 people in the US before February, and three million people are heading into Thanksgiving with active infections.

Statistics like these can numb us. The nation is exhausted and wounded, desperate for normalcy. But no matter our fatigue, we can’t forget the tragedy of every death, each an immeasurable loss for families and friends left behind. Even as promising vaccine research gives us hope, we must continue to do our part to reduce the spread of COVID-19 in the difficult months ahead. Every life we save, together, will make these efforts worthwhile.

So please—for yourself, your family, your community, and your country—stay home, stay safe, and mask up.