"And that is because the masks actually protected not only against coronaviruses but also against the influenza viruses as well". The most important thing you can do is stay at home right now, and we don't want people to feel like, "Okay, I'm covering my face, so now it's okay for me to go out in public", Surgeon General Dr. Jerome Adams told NBC News.
Cloth masks are less effective than medical masks, but their use, even if imperfect, is better than nothing at helping limit the spread of the virus.
Here's the guidance on masks as it stands.
"This worries us and that's why the debate is continuing about the mask", she said.
The CDC has only been recommending wearing a mask if you're sick or are a healthcare worker, but data shows transmission of the virus can happen with people who show no symptoms at all.
Scientists don't yet understand all of the details of how the coronavirus spreads, but they believe that it's most likely spread by droplets, little beads of saliva and mucus that surround the virus.
-Why is the WHO's guidance being reviewed? The formal announcement was expected as soon as Friday. And on Thursday the United States authorities said more than 1,000 had died in the past 24 hours - the highest daily toll so far in the world.
At what has become a daily briefing by the president and his advisers, Birx, a highly respected expert in global health, has served the role of explainer, walking journalists and the public through the data behind federal recommendations created to slow the virus's spread.
"Universal use of face masks could be considered if supplies permit".
"Because if they're touching things-remember your eyes are not in the mask - so if you're touching things and then touching your eyes you're exposing yourself in the same way".
Those using a mask should avoid touching it while wearing it and remove via the elastic straps that go over the ears and immediately wash their hands once it has been removed and disposed of. The shortage of N95s is still a serious, deadly problem for healthcare workers.
He said he suggested his wife wear one to the grocery store when she asked.
Thomas Inglesby, director of the Johns Hopkins Centre for Health Security, issued a recommendation to wear non-medical face coverings when going into public places.
New Zealand's Ministry of Health says it is keeping close watch on a review by USA authorities into whether wide use of masks could reduce the spread of Covid-19.
"And the administration with the local Dept. of Public Health and the expertise that they have", she said.
This week, Gateshead Foundation NHS Trust issued a plea on social media asking for local businesses to donate protective equipment while some Global Positioning System reported placing orders on Amazon.
Trump said states should have done more to stockpile medical supplies before the pandemic.
Communities Secretary Robert Jenrick said there was a "military operation" ongoing to move stocks around the country, with national distribution companies drafted in to help. "If people wanted to wear them, they can", Trump said.
However, Angell added that the mere sight of a face mask in public can remind others to keep their distance and discourage wearers from touching their own faces.
In Europe, Austria, Slovakia, the Czech Republic and Bosnia-Herzegovina have introduced these measures.
China bought up masks and other personal protection equipment supplies in other countries when it was in the midst of the virus crisis.
To ensure that air doesn't flow between the mask and the skin, it should be as tight as possible.
The White House is expected soon to advise Americans living in coronavirus hotspots to wear cloth masks or scarves in public to help stop the spread of the coronavirus. "They're really flat, and I think that's what you meant".
They welcomed news of an imminent advisory.
Wearing a mask could act as an another preventative measure, along with other health precautions-including social distancing, washing hands, and staying home if sick.