Face mask can cut risk of infection to wearer by 65%, says US health expert

New research suggests increased protection for those wearing facial coverings, not just reducing spread

People wearing face masks for fear of the coronavirus at the Mamilla mall in Jerusalem, on July 6, 2020. (Olivier Fitoussi/Flash90)
People wearing face masks for fear of the coronavirus at the Mamilla mall in Jerusalem, on July 6, 2020. (Olivier Fitoussi/Flash90)

Wearing a facial covering can decrease a person’s risk of becoming infected with SARS CoV-2, the virus that causes COVID-19, by 65 percent, according to an American expert in infectious diseases.

Health officials across the world have stressed the importance of wearing a face mask to reduce the rate of transmission of the novel coronavirus, but a range of new studies suggests the facial covering can reduce the risks to the wearer as well, said Dr. Dean Blumberg, chief of pediatric infectious diseases at University of California Davis Children’s Hospital.

Citing new research — including a meta-analysis on social distancing and facial coverings published last month in The Lancet, a peer-reviewed medical journal — Blumberg said: “We’ve learned more due to research and additional scientific evidence. What we know now is that masks work and are very important.”

“So the wearer of the mask, even the standard rectangular surgical masks … will decrease the risk of infection by the person wearing the mask by about 65 percent,” Blumberg said during a July 2 livestream hosted by UC Davis on how the virus spreads. Homemade masks, he added, also “should work quite well.”

Blumberg spoke alongside William Ristenpart, a professor of chemical engineering at UC Davis, and the co-author of an April paper published in the journal Aerosol Science and Technology on transmission via aerosol particles. During the interview, the two experts repeatedly emphasized the importance of social and physical distancing and facial coverings in their comments to viewers.

Masks are an effective barrier to respiratory droplets, which are one-third the size of a human hair and one of two primary methods of transmission, Blumberg said. The second is aerosol particles produced by speech, which are about 1/100th the size of a human hair.

Healthcare workers carry out testing at a Clalilt health center in Modi’in, on July 7, 2020 (Yossi Aloni/FLASH90)

“Everyone should wear a mask,” Blumberg said during the interview. “People who say, ‘I don’t believe masks work,’ are ignoring scientific evidence. It’s not a belief system. It’s like saying, ‘I don’t believe in gravity.'”

“People who don’t wear a mask increase the risk of transmission to everyone, not just the people they come into contact with. It’s all the people those people will have contact with. You’re being an irresponsible member of the community if you’re not wearing a mask. It’s like double-dipping in the guacamole. You’re not being nice to others.”

When it comes to aerosol particles, Ristenpart said that “studies in laboratory conditions now show the virus stays alive in aerosol form with a half-life on the scale of hours. It persists in the air.”

“That’s why you want to be outdoors for any social situations if possible. The good air flow will disperse the virus. If you are indoors, think about opening the windows. You want as much fresh air as possible,” he added.

Both experts warned against indoor areas like bars and being in close proximity to others.

“If you’re going past someone very quickly in a grocery store,” Blumberg said, “the risk of getting infected is very low. It’s really lingering and talking that does it.”

“It’s really important to know that just because you’re standing 6 feet or 7 feet away [1.8-2.1 meters], if you have a prolonged conversation, there is still a risk. These aerosols can be carried along on weak air currents,” added Ristenpart.

With children, Blumberg said they are less likely, by half, to be infected if they are exposed, and less likely to be symptomatic or to have a severe case if they do get sick.

“They appear to be less likely to infect others,” he said. “This is different from other infections like the flu when they are carriers. This appears to be much more of an adult disease. But children can still get sick and can still transmit it to others, so it’s important to be as hygienical with them as their development allows.”

Israeli school children wear face masks to help prevent the spread of the coronavirus as they walk in Tel Aviv, on July 6, 2020. (AP Photo/Sebastian Scheiner)

A separate May study on aerosols suggested that speech can generate thousands of mini-droplets that, in a closed environment, can hang in the air for up to 14 minutes and lead to transmission of SARS CoV-2. The research was published in The Proceedings of the National Academy of Sciences, a peer-reviewed multidisciplinary scientific journal and the official journal of the US National Academy of Sciences. According to the study, speech droplets by asymptomatic carriers “are increasingly considered to be a likely mode of disease transmission.”

On Friday, the World Health Organization urged countries grappling with the coronavirus to step up control measures, saying it was still possible to rein in the scourge. Many countries, including Israel, are seeing a resurgence of the pathogen and increased levels of infections.

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