Mask Hoarders May Raise Risk of a Coronavirus Outbreak in the U.S.

Even though there are only five cases of Wuhan coronavirus in the United States, the mask hoarding has begun.

Some pharmacies report being entirely sold out of masks. Some popular sellers on Amazon say deliveries will be delayed for weeks.

Although masks actually do little to protect healthy people, the prospect of shortages created by panic buying worries some public health experts.

Masks are thought to slow the spread of disease when they are worn by sick people in crowded places like emergency rooms, offices, subways and buses. By containing coughs and sneezes, masks stop virus-laden droplets from being spewed into the air and onto nearby surfaces.

But hoarding by those who are well means that hospitals, clinics and doctors’ offices could run short. Doctors and nurses treating patients for respiratory infections should wear masks and replace them often — as soon as they become soggy, the Centers for Disease Control and Prevention says.

The C.D.C. is now reaching out to manufacturers to head off the possibility of shortages, especially in hospitals, an agency official said.