WASHINGTON: The US government has begun advising people to wear masks if they go outside, pointing to research that shows the coronavirus could be spread just by breathing.
The advice came as America logged another huge rise in its death toll -- almost 1,500 in one day -- and as new infections continued unabated.
With 1,480 deaths counted between 8:30 pm (0030 GMT) Thursday and the same time Friday, according to the university's continuously updated figures, the total number of people who have died since the start of the pandemic in the United States is now 7,152.
It also came as China -- the origin of the outbreak -- held a national day of mourning for its citizens killed by the disease.
Since COVID-19 emerged late last year, around 1.1 million people have fallen ill.
Almost 60,000 people have died.
Europe accounts for the lion's share of the dead, with Italy and Spain bearing the brunt.
But the situation is rapidly deteriorating in the United States, and President Donald Trump's administration on Friday suggested widespread use of simple masks or scarves might help stem the rocketing infection rate.
"It's going to be really a voluntary thing," he said.
"You don't have to do it and I'm choosing not to do it, but some people may want to do it and that's okay."
Anthony Fauci, head of infectious diseases at the National Institutes of Health, cited "recent information that the virus can actually be spread even when people just speak as opposed to coughing and sneezing".
The World Health Organisation has been more cautious, saying the airborne threat was only known to occur during certain medical treatments.
The US recommendation will likely worsen an already severe shortage of masks in the United States and Europe, which both rely heavily on imports from China.
Officials in New York, the worst affected part of the US, began advising people to wear masks some days ago, and there were signs on the streets that the advice was being heeded.
"I am trying to protect me and my family. If everybody protects themselves, it's better for all of us," Eddie Marrero, a 58-year-old handyman, told AFP.
Around 277,000 Americans have tested positive for the disease, and the infection curve shows no sign of flattening, despite nine in ten citizens living under some sort of lockdown.
Field hospitals are sprouting in convention centres, sports arenas and parking lots all over the country as states gird for an expected influx of patients.