Everyday Science

Research Shows An Unexpected Benefit of Universal Mask-Wearing

Masks may not just prevent you from spreading or getting the virus. Now, a growing stack of evidence seems to say that a mask can reduce the severity of infection.
written by E Rosalie

Masks may not just prevent you from spreading or getting the virus. Now, a growing stack of evidence seems to say that a mask reduce the severity of infection. If so, that could make a mask more powerful than any therapeutic. 

How could a mask do that — the proof would have to be strong, to say such a thing, right? Yes. 

Dr. Monica Gandhi, an infectious disease specialist and professor of medicine at the University of California at San Francisco, has that evidence in spades.

She offers three categories of evidence:

  1. Virology
  2. Outbreaks with and without masks
  3. Country-level comparisons

The Percentage of Americans at Risk for Serious Illness or Death from COVID-19 Is High

The CDC estimated as of July 10, 2020, that 40% of infected people had no symptoms. As we’ve learned, the good and the bad of this is that many people don’t fall ill, but the bad part is that they can spread it to those who will fall ill or die.

About 47% of Americans fall into the high-risk group. In fact, we may have one of the highest risk populations on earth because obesity tops the lists for pre-existing conditions that increase the risk of severe Covid in all ages.

Initially, we wondered if the lower death rates in countries like South Korea could have reflected their much more aggressive initial testing. When you find the contacts of people known to have the virus and test them, then you catch more of the mild cases. 

Missing mild cases makes it seem like there are more severe cases than reality, but differences in testing don’t appear to explain all of it. The evidence says masks may have gifted us an unexpected benefit. 


Filtering the Virus

No matter the mask type, including textile masks, wearing one will filter a majority of viral particles, according to Gandhi. Whether the concern is a virus traveling inward or outward, a mask stands a good chance of stopping the virus.  

Tests with animals show that number of viral particles that infect you matters. Think of it as a dose where a high dose has more impact than a low dose. Animals infected with more virus particles got sicker than animals given fewer.

Enter, hamsters. Hamsters appear to be the best stand-in for a human. That no one published a picture of a hamster wearing a mask with their studies may be one of the great injustices of our time — don’t worry. I wrote to them about my grievances.

Why Would the Number of Viruses Matter?

Outbreak Studies

A Tale of Two Cruise Ships 

The Diamond Princess cruise ship, the location of one of the earliest outbreaks in a contained setting, had a high rate of infections with symptoms. Most people who caught the virus felt sick. Only 18% of people were asymptomatic, but no masking took place either.

On an Argentinian cruise ship the story differed. The cruise line gave everyone masks, and then there was an outbreak.

Everyone in the crew and the guests wore the masks. An outbreak study showed that the rate of asymptomatic infection skyrocketed to a shocking 81%.

Next to the 18% asymptomatic cases on the Diamond Princess, that’s stunning.

American Studies 

In Oregon, a seafood processing plant and a chicken processing plant in Arkansas, workers wore masks preemptively.

It’s important to note the outbreaks still happened. This virus is that infectious, but the masks appear to have increased the asymptomatic cases dramatically.

For both locations, 95% of people infected had no symptoms and they developed immunity that should protect them long enough for us to get a vaccine.

This drives home the power of masking. It may be more powerful than distancing.

Another example, comes from an outbreak in Indiana where all patients and staff wore masks. A single symptomatic patient exposed the staff who caught the virus and developed antibodies. The twist is that none of the  new infections had any symptoms.

Gandhi said, “I feel confident going out in public with the mask.” Indeed, her research suggests we all should breathe a little easier donning a mask.

The most dramatic example supporting this idea comes from two hairstylists in Missouri. Their employer required they wear masks, and the two tested positive after exposing 140 people together.  No one tested positive or reported a symptomatic infection, and one stylist infected people in her personal life. 

Still, customers close to her face did not fall ill. 

Masking Countries

Asian countries that experienced SARS and MER, two of the closest relatives of the virus that causes COVID-19, had partial mask-wearing in their culture already. These included Hong Kong, Singapore, Taiwan, Vietnam, and Thailand, Japan, and parts of China. Many in Asian countries wear masks when they feel unwell out of consideration for others. Masks, not worn for pollution, most often appear on the faces of people who feel sick.

Many of these countries opened society, with universal mask-wearing. Outbreaks still happened. That’s important to note. 

The key difference between those countries and the US is the death rate. In the US, the death rate is well above 1% (at least 180 thousand people died and we have at least 2 million recovered cases, or 8.6% of concluded cases ending in death), though the proportion of severe cases is likely somewhat inflated by trends that happened in the early outbreak period. 

A Considerate Man

Perhaps, the single most notable case report detailed a man who flew from China to Toronto. He had a cough, and because he came from a culture where they wear masks when sick to protect others, he wore a mask. All twenty-five people seated close to him tested negative

Taiwan, a country of 23 million, has had seven deaths in total. Seven. 

Taiwan has been open for months, though everyone is still wearing masks. Acceptance wasn’t the case everywhere.

Western societies saw this as an infringement on personal rights noteworthy: masks were common in 1918 and during the polio outbreaks. Supreme Courts ruled that  the state had the power to issue such measures. The founding fathers penned the document in a time of outbreak, so it only makes sense they planned for dealing with them.

Georgia Tech football game with fans wearing masks packed in a campus stadium during pandemic of 1918

The Double-Edged Viral Sword

The problem with asymptomatic infection is that you can pass it on if you’re not wearing a mask, but the good thing about it is that people without symptoms are unlikely to spread the virus wearing a mask.

The point of the CDC’s initial recommendations to our country on April 3, to say that we should wear masks out in public was actually to prevent people from giving it to others and not protection.

We know now that it offers some protection to the wearer. That means mask wearing protected you and those around you. The good news doesn’t stop there. 

The icing on the cake is if you catch the virus while wearing a mask, your chances of severe illness and death go down–possibly way down.

That may be better news than a vaccine because we can do that now. No production fiasco or conundrum to answer. Find one where you are, wear it, and in 2 to 4 months, our country looks like an entirely different place. That’s something on which one can really hang their hope. 

Dragging our feet is crushing our economy and mental health. We have the power to end it. We can do it now.


Main References:

Gandhi, M., Beyrer, C. & Goosby, E. Masks Do More Than Protect Others During COVID-19: Reducing the Inoculum of SARS-CoV-2 to Protect the Wearer. J GEN INTERN MED(2020). https://doi.org/10.1007/s11606-020-06067-8


Audio References: 


Sharfstein, Joshua, and Monica Gandhi. “Asymptomatic Infection with COVID-19.” Public Health On Call, The Johns Hopkins University, 21 Aug. 2020, johnshopkinssph.libsyn.com/142-asymptomatic-infection-with-covid-19?tdest_id=1899134.


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