People in the United States have been warned that they may need to stay home for an extended period to help contain the spread of the new coronavirus.

"I cannot see that all of a sudden, next week or two weeks from now it's going to be over. I don't think there's a chance of that. I think it's going to be several weeks," Dr Anthony Fauci, head of the US National Institute of Allergy and Infectious Diseases, said during an interview with the TODAY show on Friday morning.

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Millions of Americans have adjusted to near-total closures of bars and restaurants, except in the case of takeaway and delivery, school cancellations and work-from-home arrangements.

Others have lost their jobs or main sources of income, especially those in the service and travel industries.

This will not change soon, according to Fauci. "If you look at the trajectory of the curves of outbreaks and other areas, [it’s] at least going to be several weeks," Fauci said.

Stay home

While the Centers for Disease Control and Prevention has recommended all public events be cancelled and limit groups to 10 or less, states and local authorities across the US have ordered businesses to close.

California on Thursday night ordered its 40 million residents to stay home indefinitely and venture outside only for essential jobs, errands and some exercise.

"I can assure you home isolation is not my preferred choice, I know it's not yours, but it's a necessary one," Governor Gavin Newsom said at an evening news conference streamed on social media.

California is the first US state to adopt such a sweeping measure to curb the rapidly spreading coronavirus outbreak.

Newsom said Californians "can still take your kids outside, practising common sense and social distancing. You can still walk your dog". Restaurant meals can still be delivered to homes.

European nations such as France and Spain, two of the hardest-hit, have adopted similar measures.

Still, Spain's death toll surged past 1,000 on Friday, and Italy's is nearing 3,500, outpacing China, where the outbreak began.

The US is also gearing up for a shortage of hospital beds and medical supplies.

New York City Mayor Bill de Blasio and Newsom have called on the administration of President Donald Trump to use the powers granted to him by the Defense Production Act of 1950, invoked this week, which allows the president broad powers to require manufacturers to boost production of medical goods.

De Blasio has warned that if nothing is done, New York City will be out of medical supplies in "weeks".

Trump promised during a briefing on Tuesday that his administration is doing everything it can to stop the virus.

"If we do this right, our country - and the world, frankly - but our country can be rolling again pretty quickly. Pretty quickly," he said.