Fears of a coronavirus pandemic have spurred a run on face masks worn to reduce chances of inhaling airborne virus from someone else’s coughs and sneezes.

Store shelves are empty and so are the stockrooms of online e-tailers, from the mighty Amazon to drug store chains like CVS.

Now what? Well, for the record, the U.S. Centers for Disease Control and Prevention doesn’t recommend face masks for those who aren’t sick or caring for someone with the disease. Instead, just keep your distance (six feet) from others, cover your nose and mouth if you cough or sneeze, wash your hands and stay home if you’re not well.

Experts say that’s sound guidance.

“At present, the level of risk in the U.S. is very low, and routine wearing of masks is not indicated,” said Dr. Peter Rabinowitz, a University of Washington professor of environmental and occupational health sciences, family medicine and global health. “Masks in general are not the first line of defense against respiratory infections. Much more important are frequent hand-washing, keeping your distance from people who are sick and coughing, and if you are sick, staying home or if necessary wearing a mask to avoid coughing as many droplets into the air.”

There are also different kinds of masks that have different levels of effectiveness. The most effective is the N 95 respirator, government certified to filter out at least 95 percent of microscopic airborne particles, including viruses. They often are aimed at industrial workers to protect them from airborne particles, but also are made for hospital workers and the general public.

The respirators only work if they fit tightly around the nose and mouth — which can be tricky — and they aren’t suitable for children or fully bearded men.

Surgical masks offer less protection. They fit loosely around the nose and mouth, and fine, virus-laden airborne particles could be inhaled with unfiltered air around their edges. So a makeshift substitute like a bandanna or handkerchief that fits more loosely will filter out even fewer particles.

“Surgical masks provide less protection than N95 masks, and my guess is that bandannas would provide even less,” Rabinowitz said.

Denise McPherson, Nurse Practitioner at Dignity Health-GoHealth Urgent Care, said the surgical masks are chiefly designed to prevent a person from spreading a respiratory illness to others, but do not prevent the person wearing the mask from bacteria or viruses in the air.

“If you think you have a respiratory illness, a surgical mask would be the best item to wear to decrease the spread to others,” McPherson said. “If you are well, but around someone with a respiratory illness, then a respirator mask would be the best item to wear to decrease the chance of contracting the illness.”

And to be sure, McPherson added, “handkerchiefs, bandannas, and other articles of clothing do not have the barriers needed to protect someone from spreading illness or from contracting illness.”

The masks also are designed to be disposable. Eventually, they clog up and must be disposed. And if you think they protected you from some viral air, be careful how you handle them.

“One problem is that masks can become contaminated on the outside, and when you touch them, you can contaminate your hands,” Rabinowitz said.

How effective are the masks? They offer some protection, which is why hospital workers use them, but there are few conclusive studies on their effectiveness when worn by the general public.

Dr. Arnold S. Monto of the University of Michigan’s Department of Epidemiology and School of Public Health said the loose-fitting surgical masks “are modestly effective — the problem is they are not nearly as effective as the N 95 respirators.”

Monto said the most effective measure is simply keeping your distance from others.

“The thing that really seems to work on this,” Monto said, “is social distancing.”