Which masks should health care professionals be using?

Ideally, clinicians would be using a new, tightly-sealed respirator, like the N95, with each patient. These are thicker than standard surgical masks, and are designed to fit more tightly around the mouth and nose to block out much smaller particles. The Food and Drug Administration said that neither surgical masks nor N95s should be shared or be reused.

As the outbreak worsened and there were shortages in medical supplies across the country, the C.D.C. updated its recommendations for optimizing the supply of protective gear.

Now, except in the case of intubations, which involve inserting a breathing tube, the agency says standard surgical masks are acceptable when examining or treating a coronavirus patient. (This aligns more closely with the W.H.O., which advises that surgical masks can be used in some situations, but warns that they are not sufficient on their own.)

Some medical professionals suggested that the C.D.C.’s new recommendations are borne of political expediency instead of science.

“We are concerned that C.D.C. recommendations are based solely on supply chain and manufacturing challenges,” the American Nurses Association said in a public letter.

Now, the C.D.C. also outlines a crisis strategy for wearing the same mask for repeated encounters with different patients. It suggests medical professionals may need to use masks beyond the manufacturer-designated shelf life date, and to prioritize the use of masks for activities in which there may be sprays, splashes or prolonged exposure.

“As a last resort,” the C.D.C. says “homemade masks” like a bandanna or a scarf can be used, although their protective ability is unknown.