China paid homage Saturday to victims of the coronavirus in the place where the global pandemic began, as Americans were warned to wear masks amid fears the disease can be spread 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.
Since COVID-19 emerged late last year, around 1.1 million people have fallen ill. Almost 60,000 people have died.
China, which appears to be over the worst of its outbreak, on Saturday held a national day of mourning for its dead -- well over 3,000 people have died since the virus emerged there late last year.
Cars, trains and ships sounded their horns, and air-raid sirens wailed, as flags were flown at half-staff from 10 am (0200 GMT).
Beijing has said the observance is a chance to mourn virus "martyrs" -- an honorific title bestowed by the government this week on 14 medical workers who died fighting the outbreak -- including the man who was punished by officials for raising the initial alarm.
"I feel a lot of sorrow about our colleagues and patients who died," said Xu, a nurse who worked on the front lines in the central city of Wuhan, where the virus was first detected.
"I hope they can rest well in heaven."
"It's going to be really a voluntary thing," Trump 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 COVID-19 storm is now coming to all these theaters of conflict."