NEW YORK/PALO ALTO, U.S. -- The Trump administration reversed its position on face masks Friday and made clear that it now recommends the use of cloth face coverings to stem the spread of COVID-19.
The administration had previously suggested that healthy people should not use masks.
President Donald Trump emphasized that the new recommendation should not be seen as replacing social distancing measures.
"This is voluntary," Trump said of mask-wearing. "I don't think I'm going to be doing it."
By way of explanation, he cited high-profile meetings in the White House. Wearing a mask "as I greet presidents, prime ministers, dictators, kings, queens ... somehow, I don't see it for myself," he said.
The decision to promote mask use comes as state governors and hospitals clamor for scarce supplies of medical-grade masks for first responders. It also comes as experts have questioned the administration's decision not to urge widespread mask use, in contrast to other virus-hit countries.
"What has changed in our recommendation?" U.S. Surgeon General Jerome Adams said at the White House briefing. "Well, it's important to know that we now know from recent studies that a significant portion of individuals with coronavirus lack symptoms, they're what we call asymptomatic."
People can "transmit the virus to others before they show symptoms," he said.
This marked a shift from a Feb. 29 tweet where Adams had urged the public to "STOP BUYING MASKS!"
"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 had written.
Adams explained at Friday's briefing that "based on the best evidence available at the time, it was not deemed that that would have a significant impact on whether or not a healthy person wearing a mask would contract COVID-19."
A late acknowledgment of widespread asymptomatic transmission of COVID-19 has also been behind other aspects of the slow U.S. response to outbreak.
Georgia Gov. Brian Kemp and New York City Mayor Bill de Blasio this week both claimed to have only recently learned that the coronavirus can spread through carriers without symptoms.
Kemp on Wednesday called the information a "game changer" that has led him to issue a stay-at-home order in his state. Georgia had reported close to 5,000 cases by then.
In New York, the epicenter of the outbreak in the U.S., the Department of Health and Mental Hygiene on Thursday began advising that residents wear "a face covering" when they venture outside the home and will be near others.
"I want to emphasize this ... the reason for this guidance is because the studies are showing that some asymptomatic people, some presymptomatic people, appear to actually be transmitting this disease," de Blasio said in his daily briefing.
The city defines "face covering" as "any well-secured paper or cloth (like a bandana or scarf) that covers your mouth and nose."
"There is a lot we are still learning about COVID-19," the NYC guidelines explained about the new recommendation. "However, there is increased evidence that people without symptoms may be able to spread the virus, and that droplets produced when breathing, speaking, or singing may spread COVID-19 from person to person."
At the same time, NYC still does not recommend N95 or surgical masks, given the severe shortage.
Earlier this week, California became the first U.S. state to officially recommend that members of the general public cover their faces, acknowledging that it could help prevent the spread of the coronavirus.
"The use of cloth face coverings could reduce the transmission of COVID-19 by individuals who do not have symptoms and may reinforce physical distancing," the California Department of Public Health said when announcing new guidance Wednesday to supplement its existing advice on social distancing and hand-washing.
It said the state does not recommend that the general public wear N95 or surgical masks, which are needed for health care workers and first responders and are now short in supply.
"Face coverings are not a substitute for physical distancing or frequent hand washing, which we know are amongst the most effective ways to reduce the spread of COVID-19," said Dr. Sonia Angell, state health officer and director of the Department of Public Health, in a news release.
"Wearing a cloth face covering could provide some additional benefit by acting as a reminder for other people to keep their distance, and it could help reduce the spread of infectious particles from those who could be infected but don't have symptoms," Angell added.
"Face coverings could provide some additional protection against COVID-19, but Californians should not have a false sense of security if they choose to wear them," California Health and Human Services Secretary Dr. Mark Ghaly said in the release. "Make sure you're also staying 6 feet away from other people if you have to leave your home to get groceries or prescriptions."
Meanwhile, southern California's San Diego County is breaking new ground by mandating employee face coverings at businesses that interact with the public. The requirement applies to grocery stores, convenience stores, restaurants, pharmacies and gas stations.