WASHINGTON — The Trump administration is expected to recommend that all Americans wear cloth masks if they go out in public, a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms.
Until now, the federal Centers for Disease Control and Prevention, like the World Health Organization, has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks, including N95 respirator masks, for health care workers who desperately need them at a time when they are in continuously short supply.
But according to a federal official, the C.D.C. will now recommend that everyone wear face coverings in public settings, like pharmacies and grocery stores, to avoid unwittingly spreading the virus. Public health officials have stressed that N95 masks and surgical masks should be saved for front-line doctors and nurses, who have been in dire need of protective gear.
Asked about the changing guidance at Thursday’s coronavirus task force briefing, President Trump was somewhat ambiguous, saying that it “will not be mandatory because some people don’t want to do that.” He added, “If people want to wear them, they can. If people want to use scarves, which they have, many people have them.”
As coronavirus cases have spread across the country, the Trump administration has had shifting positions on whether regular citizens should cover their faces in public.
“Seriously people — STOP BUYING MASKS!” the surgeon general, Dr. Jerome M. Adams, said in a tweet in late February. “They are NOT effective in preventing general public from catching #Coronavirus, but if health care providers can’t get them to care for sick patients, it puts them and our communities at risk!”
He was most concerned about widespread hoarding of the tightfitting N95 masks that can stop infectious particles even finer than a micron in diameter, and that even many health care workers have not been able to find.
But earlier this week, Mr. Trump said that broad use of nonmedical masks, at least, was “certainly something we could discuss.”
Dr. Robert Redfield, the director of the C.D.C., confirmed in a radio interview earlier this week that the agency was reviewing its guidelines on who should wear masks. Citing new data that shows high rates of transmission from people who are infected but show no symptoms, he said the guidance on mask wearing was “being critically re-reviewed, to see if there’s potential additional value for individuals that are infected or individuals that may be asymptomatically infected.”
On Wednesday, Mayor Eric Garcetti of Los Angeles urged all of that city’s residents to wear homemade nonmedical face coverings, or even bandannas, when food shopping or doing other essential errands. Health officials in Riverside County, Calif., made a similar recommendation on Tuesday.
The federal official said the C.D.C.’s revised guidance stemmed from a request by the White House and the task force.
While wearing masks to prevent the spread of disease is a widely accepted practice in many Asian countries, it remains to be seen how Americans will react to the new recommendation. But a growing number of public health experts have been recommending universal mask use.
A recent white paper from the American Enterprise Institute had argued the move could have substantial public health benefits. One of its authors, the former F.D.A. commissioner Scott Gottlieb, had been forcefully advocating for the policy in media appearances.
And a white paper from a group of Yale researchers released on Thursday estimated that universal mask use could reduce infections by around 10 percent, creating a value of $3,000 to $6,000 per American, based on estimates of the value of saved lives. The authors included Sten H. Vermund, the dean of the Yale School of Public Health, and Albert Ko, the chairman of Yale Medical School’s department of epidemiology and microbial diseases.
Both papers recommended that members of the public wear homemade cloth masks, to preserve limited supplies of surgical masks and higher-grade respirators for health care workers.
“It is critically important that public adoption not come at the expense of medical mask availability for health workers,” said Jason Abaluck, an associate professor of economics at the Yale School of Management and a co-author of the paper. “This is why we emphasize universal adoption of cloth masks.”
The researchers emphasized that the primary benefit of mask wearing was to prevent infected people from spreading the virus by expelling infected droplets.