There is a common refrain that masks do not protect you; They protect other people from their own germs, which is especially important to prevent infected people from unknowingly transmitting the coronavirus.
But now, there is mounting evidence that masks also protect you.
If you are unlucky enough to meet an infectious person, wearing any type of facial covering will reduce the amount of virus your body will absorb.
It turns out that that’s pretty important. Breathing a small amount of virus can lead to the absence of disease or a much milder infection. But inhaling a large volume of virus particles can cause serious illness or death.
That’s the argument of Dr. Monica Gandhi, UC San Francisco professor of medicine and medical director of the HIV Clinic at Zuckerberg San Francisco General Hospital, about why, if you are not fortunate enough to become infected with the virus, the masking can still protect you from more severe disease
“There is this theory that facial masking reduces the [amount of virus you get exposed to] and the severity of the disease, “said Gandhi, who is also director of the AIDS Research Center at UC San Francisco.
The idea of requiring the wearing of masks in public has become an increasingly urgent and politicized issue as California and the rest of the nation see an increase in new cases as the economy reopens.
This week, California ordered the closure of many businesses, including the shutdown of all meals indoors and the closure of bars across the state. The state also ordered the closure, in dozens of heavily affected counties, including Los Angeles County, of indoor gyms, houses of worship, beauty salons, beauty salons, and offices for nonessential industries.
But experts say the masks are essential for people to wear when they’re still out in the public, like shopping or going to medical appointments, and exercising like going to the beach or the park.
California has ordered covering its face in public places since June 18, and a growing number of communities said it will fine people who break the rules. But there is still some resistance to the government that requires the use of masks in some corners of the state, including Orange County.
Some leaders in Orange County have refused to require students to wear masks if they return to classrooms in the fall.
In policy recommendations approved by the Orange County Board of Education on Monday, a document states that “requiring children to wear masks during school is not only difficult, if not impossible to implement, but [is] Not based on science. It can even be harmful. “Individual districts will have the last word on how schools open.
Some health experts were horrified by that language.
“This anti-mask rhetoric is mind-blowing, dangerous, deadly, and polarizing,” said Dr. Peter Chin-Hong, professor of medicine and infectious disease specialist at the University of California, San Francisco. “There is no evidence that it is dangerous.”
In fact, wearing masks can help prevent children from becoming infected and suffering serious consequences from the infection, such as multi-system inflammatory syndrome, a rare condition that has been observed in children who have been infected with the coronavirus. “Children not only transmit, but they can also get sick,” said Chin-Hong.
While children are less likely to develop severe coronavirus disease than adults, they can still become infected, catch and pass the virus on to others, Gandhi said.
Wearing a mask at school would not only reduce their ability to transmit the virus to other classmates, teachers, and administrators, but would also protect students from becoming infected with a large dose of virus from infected people.
Coronavirus transmission rates have increased across the state. Nearly 1,000 of San Francisco’s nearly 4,600 cases have been diagnosed in the past two weeks, said Dr. Grant Colfax, the city’s director of public health.
In San Francisco, almost half of all those who tested positive in the city are Latinos, he said, even though Latino residents represent only 15% of the city’s population. Overall, the city has seen 7.8 new infections per 100,000 residents in the past seven days, well above its target of no more than 1.8 new infections per 100,000 people.
“This, again, indicates that the virus is spreading throughout the city, particularly … in the southeast part of the city,” Colfax said.
He said that for every person who contracts the virus, another 1.25 people on average are now infected. “We really need to reduce that to 1 or less as fast and as soon as possible.”
The transmission rate also rose above 1 in Los Angeles County in June, but fell again to 1. “The virus is currently unleashing in our community,” said director of public health Barbara Ferrer.
The reason masks are so important in controlling the spread of the coronavirus is that it can be widely spread by people who are not visibly ill, either because they have not yet shown signs of illness or because they will spend the entire course of their illness. infections with little or no symptoms at all.
Key evidence of this emerged earlier this year, on the Diamond Princess cruise ship carrying infected crew and passengers in Asia. A study published by the US Centers for Disease Control and Prevention found that of 712 people who tested positive for the virus, nearly half were asymptomatic at the time of the test.
“We also know that viral load is highest early in the disease,” said Dr. Chaz Langelier, an assistant professor at UC San Francisco, during the roundtable. In fact, 44% of transmissions are believed to occur when the infected person has no symptoms, according to a study published in Nature Medicine.
That’s different from seasonal flu, where peak infectivity occurs about a day after symptoms start, Langelier said.
Masks do not filter out all viral particles, Gandhi said. But even cloth masks filter out most viral particles.
And even if a person wearing a mask becomes infected, the mask, by filtering out most of the viral particles exhaled by the infected person, probably leads to less serious illness, Gandhi said.
The idea that a lower dose of virus when infected causes fewer diseases is a widely used idea in medicine.
Even since 1938, there was a study that showed that by giving mice a higher dose of a deadly virus, mice are more likely to contract serious diseases and die, Gandhi said.
The same principle applies to humans. A study published in 2015 gave healthy volunteers varying doses of a flu virus; Those who received higher doses became ill, with more coughing and shortness of breath, Gandhi said.
And another study suggested that the reason the second wave of the 1918-19 influenza pandemic was the deadliest in the US was due to overcrowded conditions in army camps when World War I ended. .
Finally, a study published in May found that surgical mask partitions significantly reduced coronavirus transmission among hamsters. And even if the hamsters protected by the mask partitions acquired the coronavirus, “they were more likely to contract very mild disease,” Gandhi said.
So what happens if a city dramatically masks itself while in public?
If Gandhi is right, it may mean that even if there is an increase in coronavirus infections in a city, masks can limit the dose people receive of the virus and increase the likelihood that they will develop less severe symptoms of the disease.
That’s what Gandhi said he suspects is happening in San Francisco, where wearing masks is relatively robust. More observations are needed, Gandhi said.
There is more evidence that masks can be protective, even when users become infected. She cited an outbreak at a seafood plant in Oregon where employees received masks, and 95% of those infected were asymptomatic.
Gandhi also cited the experience of a cruise ship traveling from Argentina to Antarctica in March when the coronavirus infected people on board, as documented in a recent study. The passengers obtained surgical masks; the crew obtained N95 masks.
But instead of about 40% of those infected being asymptomatic, which is what would normally be expected, 81% of those who tested positive were asymptomatic, and masking may have helped reduce the severity of the disease in people. on board, Gandhi said.
The protective effects are also seen in countries where masks are universally accepted for years, such as Taiwan, Thailand, South Korea, and Singapore. “Everyone has seen cases when they opened … but no deaths,” Gandhi said.
The Czech Republic stepped forward to demand masks and issued an order in mid-March, Gandhi said; That’s about three months before Governor Gavin Newsom did it throughout the state of California. But in the Czech Republic, “every time their cases increased … their death rate was totally flat. So they didn’t get serious disease with these cases.”
In May, the Czech Republic lifted its facial mask rule. “And they are doing very well,” Gandhi said.
