Stanford Medicine says vacuum cleaner bags, antimicrobial pillowcases, and other materials are reasonably effective substitutes for medical masks. Various studies point to similar results for those homemade face coverings, particularly when combined with hand-washing hygiene.

Even if masks don’t completely protect each individual, they could considerably reduce the spread of the virus. Even if the coverings only reduced transmission to and from each wearer by half, that would reduce the chance of spread by 75 percent. So face coverings could reduce the exponential growth of new infections and avert disaster in America’s hot spots.

Because scientists cannot rule out with complete confidence that this coronavirus can be spread easily in the air, even outdoors, we believe it’s most prudent to promote face covering in all public settings. And to state the obvious, mask wearing and face covering is not a substitute for shelter-in-place, hand-washing and other protective measures.

Those wearing a mask may be stigmatized, since they might be presumed to be sick, given current government guidance. A national policy on face coverings for all, even those who have had the disease, like our co-author Dr. Kass, could eliminate that stigma. Wearing masks is a way we can all protect each other.

People should be strictly warned that wearing a face covering doesn’t let you ignore social distancing rules. That would be counterproductive.

Wearing masks will not only reduce viral spread, it would also help us return to work, get back to school, and avoid what could be a devastating second wave of the coronavirus.

While ensuring that all health workers have full protective equipment, and as many essential workers as possible have medical masks, President Trump, federal health officials, governors and mayors should call on Americans in well-populated cities and towns to wear face coverings or masks in all public areas. (Government officials should start by wearing masks themselves, particularly in media appearances, to reduce the stigma and encourage use.)