For months, health officials have been walking an awkward line on masks, saying they offered little or no protection to the public and should be reserved for health care workers.

That contradiction seems close to resolution now.

The White House, while stopping short of declaring an official policy, joined the mayors of Los Angeles and New York, several European nations and much of Asia in recommending that people wear cloth face masks in public, even if they have no symptoms.

That may help stop people from transmitting the coronavirus, but social distancing remains the best way to slow the spread, health officials say. Nearly four billion people on the planet — half of humanity — found themselves on Friday under some sort of order to stay in their homes.

But some US states were still resisting such measures.

Dr Anthony Fauci, the nation’s leading infectious disease expert, said that he believed that a nationwide lockdown order made sense.

“You know, the tension between federally mandated versus states’ rights to do what they want is something I don’t want to get into,” he told CNN on Thursday. “But if you look at what’s going on in this country, I just don’t understand why we’re not doing that.”

The lockdowns have led to a collapse of the global economy, vapourising 10 million jobs in the US in just two weeks.

Global stocks, which had surged on Thursday after a wishful tweet from President Trump about the oil markets, dipped again on Friday amid growing fears that the pain will be profound and prolonged, while US equity futures pointed lower.

Governments have promised trillions of dollars in a desperate effort to limit the damage.

None of that has stopped the virus’s ferocious global assault. At least one million infections have been detected worldwide, but experts suspect the true number is far larger because of asymptomatic cases and delays in widespread testing. The Australian medical chief estimated that there are between five million and 10 million cases.

Model makers are now being guided by other grim data, most of it coming from Europe.

No country has been hit harder by the coronavirus than Italy, and no province has suffered as many losses as Bergamo. Photos and voices from there evoke a portrait of despair.

The staggering death tolls in Italy and Spain, accounting for nearly half of the 53,000 deaths worldwide, rose yet again.

But the crisis is deepening across the continent, with more than 5,000 deaths in France, nearly 3,000 in Britain, and more than 1,000 in both Germany and Belgium.

The number of recorded deaths in the US topped 1,000 in a single day for the first time. In New York City, the centre of the country’s outbreak, both hospitals and morgues struggled to meet surging demand.

Governor Andrew Cuomo warned on Thursday that time was running out to find critical supplies, including the ventilators needed to sustain the most critically ill patients.

“If a person comes in and needs a ventilator and you don’t have a ventilator, the person dies,” Cuomo said at his daily briefing in Albany.

“That’s the blunt equation here. And right now we have a burn rate that would suggest we have about six days in the stockpile.”