In another appeal on Facebook, Dr. John McCarley, a doctor in Chattanooga, Tenn., noted that local hospitals were filling up. He posted: “I’m not saying we need a lockdown but I am asking everyone to get back to a May 2020 mind-set and routinely wear the mask when indoors around others besides your household.”

In Amarillo, Texas, an internal medicine doctor said that hospitals in the city were trying to find ways to add additional I.C.U. space, and pleaded with the public to wear a mask and socially distance. “An ounce of prevention is better than a pound of cure,” Dr. Whit Walker wrote on Facebook. “I see some people inside in a public store without a mask. If you give this virus to me I might give the virus to 5 or 20 other people. One or five of those might die from the virus. Even though you feel well, you can carry this virus. Even if you had the infection in the past, you might get this same virus again. This is real. This is deadly.”