“It seems kind of intuitively obvious that if you put something—whether it’s a scarf or a mask—in front of your nose and mouth, that will filter out some of these viruses that are floating around out there,” says Dr. William Schaffner, professor of medicine in the division of infectious diseases at Vanderbilt University. The only problem: that’s not effective against respiratory illnesses like the flu and COVID-19. If it were, “the CDC would have recommended it years ago,” he says. “It doesn’t, because it makes science-based recommendations.”
The science, according to the CDC, says that surgical masks won’t stop the wearer from inhaling small airborne particles, which can cause infection. Nor do these masks form a snug seal around the face. The CDC recommends surgical masks only for people who already show symptoms of coronavirus and must go outside, since wearing a mask can help prevent spreading the virus by protecting others nearby when you cough or sneeze. The agency also recommends these masks for caregivers of people infected with the virus.
https://time.com/5794729/coronavirus-face-masks/