If 80% of people wear a mask in public, COVID-19 transmission could be halted.
Much to his surprise, Jeremy Howard, a data scientist at the University of San Francisco, discovered recently that the evidence for wearing masks in public was very strong.
“It appeared that universal mask-wearing could be one of the most important tools in tackling the spread of COVID-19,” Howard wrote on May 14 for The Conversation. “Yet the people around me weren’t wearing masks and health organizations in the U.S. weren’t recommending their use.”
Howard and 18 other experts from a variety of disciplines conducted a review of the research on public mask-wearing as a tool to slow the spread SARS-CoV-2. The group published a preprint of a paper that is now awaiting peer review at the Proceedings of the National Academy of Sciences.
Howard points to an experiment conducted at the National Institutes of Health using lasers to illuminate and count the number of droplets of saliva flung into the air by a person talking with and without a face mask. When the researcher used a simple cloth face cover, nearly all the droplets were blocked. The experiment is featured in a YouTube video.
The light-scattering experiment cannot see “micro-droplets” that are smaller than 5 microns. These smaller droplets could contain some viral particles, but experts don’t think these smaller droplets are responsible for much COVID-19 transmission.
More recent research suggests that cloth masks are also effective at reducing the spread of these smaller particles. In a paper that has not yet been peer-reviewed, researchers found that micro-droplets fell out of the air within 1.5 meters of the person who was wearing a mask, compared with 5 meters for those not wearing masks.
“When combined with social distancing, this suggests that masks can effectively reduce transmission via micro-droplets,” writes Howard.
“There are numerous studies that suggest if 80% of people wear a mask in public, then COVID-19 transmission could be halted,” Howard concludes. “Until a vaccine or a cure for COVID-19 is discovered, cloth face masks might be the most important tool we currently have to fight the pandemic.”