The debate over whether Americans should wear face masks to control coronavirus transmission has been settled. Although public health authorities gave confusing and often contradictory advice in the early months of the pandemic, most experts now agree that if everyone wears a mask, individuals protect one another.
Researchers know that even simple masks can effectively stop droplets spewing from an infected wearer’s nose or mouth. In a study published in April in Nature, scientists showed that when people who are infected with influenza, rhinovirus or a mild cold-causing coronavirus wore a mask, it blocked nearly 100 percent of the viral droplets they exhaled, as well as some tiny aerosol particles.
https://www.nature.com/articles/s41591-020-0843-2