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.