In recent weeks, facing public uncertainty about coronavirus and a severe domestic shortage of medical-grade face masks, top Trump administration officials offered adamant warnings against widespread use of masks, going so far as to argue that members of the general public were more likely to catch the virus if they used them.

“You can increase your risk of getting it by wearing a mask if you are not a health care provider,” Surgeon General Jerome Adams said during an appearance on “Fox & Friends” earlier this month.

“If it’s not fitted right you’re going to fumble with it,” warned Health and Human Services Secretary Alex Azar late last month, when asked about N95 respirator masks.

“Right now, in the United States, people should not be walking around with masks,” said Dr. Anthony Fauci, an immunologist and a public face of the White House Coronavirus Task Force, on CBS’ “60 Minutes” earlier this month. He, like the others, suggested that masks could put users at risk by causing them to touch their face more often.

But as the crisis has played out around the world and intensified in parts of the U.S., reasons have emerged to doubt the wisdom of this guidance, which ranks among the most forceful warnings against mask use by national health authorities anywhere and does not differentiate between medical-grade masks and simple cloth coverings. A number of societies where mask use is more widespread, and where mask shortages have been less severe, seem to have had more success containing the virus. Now, some health experts, who say there is no evidence for the claim that masks increase users’ risk of catching the virus, are calling for more widespread use of face coverings in the U.S.

“Guidance needs to change and needs to be clear that these nonmedical, nonsurgical masks are beneficial to the general public and should be worn when outside of the home,” said Robert Hecht, a professor of epidemiology at the Yale School of Public Health.

The increasing calls for more use of masks raise the question of whether authorities’ recommendations were based on genuine concerns about spreading Covid-19 or instead motivated by a desire to prevent a run on limited supplies of masks: “Seriously people — STOP BUYING MASKS!” tweeted Adams in late February. “They are NOT effective in preventing general public from catching #Coronavirus but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk!”