New York City Mayor Bill de Blasio told New Yorkers to cover their faces when they go outside, even if it's a homemade mask, reversing previous guidance advising only those who are sick wear face masks.
"We're advising New Yorkers to wear a face covering when you go outside and near other people," de Blasio said at a press conference Thursday. "It can be a scarf, it can be something you create at home it can be a bandana."
De Blasio cautioned residents against wearing surgical masks or other medical-grade masks, worrying that it would make the shortage for personal protective equipment in hospitals even worse.
"When you think of masks, you think of what our health care workers and first responders need and those precious supplies that we're bringing in, those PPEs, that's for them and all those people at the front line who need it," de Blasio said.
The less fancy the face covering, the better, said Dr. Oxiris Barbot, commissioner of the New York City Department of Health and Mental Hygiene. She recommended keeping more than one face covering on hand to alternate between them.
Barbot said they've changed their stance since there's wide-spread community transmission in New York City and evidence that the virus spreads before people have symptoms.
"The last 48 hours really is when our health leadership, our health department, has gotten the information and analyzed the information and provided this specific proposal so it's literally just in the last days," de Blasio said.
The Centers for Disease Control and Prevention published new research earlier this week that showed several clusters of cases in Singapore triggered by people who were completely asymptomatic.
The following evening, Trump repeated that advice, saying scarves are "highly recommended by the professionals."
"Depending on the fabric, I think in a certain way, a scarf is better," Trump said.
Doctors have warned that wearing masks in public, homemade or otherwise, can be counterproductive because they might engender a "false sense of security," leading people to practice more effective social distancing measures less carefully.
"As far as the general public is concerned, the do-it-yourself option of wearing a scarf or bandana may be the best we can do at this point," said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases.
Dr. Angela Hewlett of the Infectious Diseases Society of America said that wearing a scarf or bandana could protect others from the spread of the coronavirus. It might also keep people from touching their faces, she said.
"A scarf acts sort of like a handkerchief or a tissue," Hewlett said. "If you're wearing a scarf around your face, or another homemade mask, then there's a chance that your secretions will be contained in that as opposed to being spread to the environment."
On Wednesday, de Blasio said the city needs to find 3.3 million N95 masks, 2.1 million surgical masks, 100,000 isolation gowns and 400 ventilators by Sunday to get the city's hospitals ready for a coming wave of coronavirus patients expected by Monday.
Globally, the coronavirus has infected more than 1 million people and has killed at least 50,000, according to Johns Hopkins University data.