A new report from a hair salon in Springfield, Missouri, shows wearing a face mask isn’t just altruistic – it also helps keep the person wearing it from getting COVID-19.
And some infectious disease experts increasingly think wearing a mask could mean that even if a person is infected, they are more likely to get a milder or even asymptomatic form of the disease.
The Missouri hair salon case was published in this week’s Morbidity and Mortality Report from the Centers for Disease Control and Prevention. It’s an example of the power of face masks to stop the spread of SARS-CoV-2, the virus that causes COVID-19.
On May 12, a hair stylist at a Springfield Great Clips salon developed respiratory symptoms, but kept working for eight days until a COVID-19 test came back positive.
Another stylist started getting sick three days later and worked for another seven days before testing positive and staying home. Both colleagues wore masks only when customers were present.
Six close contacts of the first stylist ended up coming down with COVID-19. But in the salon, where 98% of clients wore masks, things played out differently. Of the 67 clients exposed to one or both of the stylists and tested for COVID-19, not one tested positive.
While cloth face coverings aren’t 100% effective, “wearing them means you’re exposed to less virus. Less is coming in from other people and you’re inhaling less. It’s a win-win,” said Dr. John Brooks, a medical epidemiologist and the CDC’s chief medical officer for the agency’s COVID-19 response.
If the American public were to embrace masking now, Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said the pandemic could be brought to heel in less than two months.
“If we could get everybody to wear a mask right now, I really do think over the next 4-6-8 weeks, I really think we can bring this under control,” he said in an interview Tuesday with the editor in chief of the Journal of the American Medical Association.
Masks could mean getting less sick
And it might do more than quell the outbreak. A hypothesis among some infectious disease experts is that those infected while wearing masks breathe in a lower dose of the virus, and as a result often have less severe illness.
A forthcoming article in the Journal of General Internal Medicine lays out the theory.
It makes a lot of sense, said Dr. Joshua Sharfstein, an expert in health policy at Johns Hopkins Bloomberg School of Public Health.
“Wearing a mask may protect the mask wearer more than we realize,” he said. “This paper provides a new explanation for lower rates of death in areas where mask wearing is common, as well as an even stronger rationale for all of us to wear masks when around others.”
The rationale is based on the medical concept of “viral inoculum,” or how much virus someone is exposed to. The evidence about viral, bacterial or fungal exposure affecting how sick someone gets goes back to the 1930s.
“We know this for gastrointestinal viruses, sexually transmitted diseases and respiratory infections. The bigger the load the more you get in your system, the more severe the disease,” said Dr. Monica Gandhi, a professor of medicine and infectious disease expert at the University of California, San Francisco and co-author on the paper.
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Wearing a cloth face covering is estimated to screen out between 65% and 85% of viral particles, said Dr. Chris Beyrer, an epidemiologist at Johns Hopkins Bloomberg School of Public Health and another author.
Depending on how robust the person’s immune system is, a smaller exposure seems to correlate with milder cases of COVID-19. It’s probably because with a smaller amount of virus to deal with, the body’s immune system has a better chance of mounting a defense, the paper’s authors suggest.
It’s seen in many other diseases, said Otto Yang, a professor of medicine and chief of infectious diseases at the David Geffen School of Medicine at UCLA
“When somebody’s infected with a virus, there’s immediately a race between the virus replicating itself and the immune system. The bigger the inoculum a person gets, the bigger head start the virus has,” he said.
It also appears people who wear masks but contract the disease are much more likely to be asymptomatic, meaning they have COVID-19 but no symptoms.
“If you’re going to get this virus, you want to have an asymptomatic infection. As so many people who’ve survived it have said, it’s not an ordinary flu. People are very sick, even those who don’t require hospitalization,” Beyrer said.
The idea remains a hypothesis because the scientists don’t have specific data, as it’s impossible to do studies in humans.
“We can’t spray SARS-CoV-2 virus in people’s faces at lower and higher doses and see who gets sicker,” Gandhi said.
But there is animal data. A study in hamsters found that if masks were used to filter the air into their cages, the hamsters were less likely to become infected with COVID-19, and if they did get infected, they had milder disease.
There’s also ecological evidence from the pandemic that seems to bear this out. Take the case of two cruise ships that both had COVID-19 onboard.
“Cruise ships in some ways are like a natural experiment,” Beyrer said. “Things were done differently on different ships and the outcomes were different.
The first was the Diamond Princess, where 18% of those who got infected with COVID-19 were asymptomatic. Very few passengers wore masks.
A later infection hit the another cruise ship, the Shackleton. When the first case appeared, all passengers were issued surgical masks and all staff wore N-95 masks. While 58% of passengers and crew ended up becoming infected with COVID-19, a full 81% of them were asymptomatic.
Another example comes from Oregon, where everyone in a fish processing plant was issued masks each day at work. While 33% of workers tested ended up being positive for COVID-19, 95% of them were asymptomatic.
In countries where a high percentage of the population wears masks, the number of cases may rise, but the number of deaths falls. Some models show that if 80% of people wear masks, death rates from COVID-19 stay very low.
In the United States, San Francisco has a very high level of mask wearing, and while cases have been going up, the death rate has remained flat. In fact, there have been no new deaths since June 27. The city also is showing a high level of asymptomatic cases.
A high level of asymptomatic cases means that fewer people are actually getting sick from COVID-19, and those that are are less likely to spread the disease.
Face masks could be key to getting back to as normal as possible before a vaccine is available. It will still require social distancing and handwashing, but masking could allow things to open up, said the CDC’s Brooks.
“What we’re saying is, if everybody will adopt cloth face coverings, we can begin socializing again without shutting down the economy,” he said.