Hospital conditions across the US are deteriorating by the day as the coronavirus rages across the country at an unrelenting pace and the death toll surpasses 250,000.

The number of people in the hospital with Covid-19 in the US has doubled in the past month and set new records every day this week.

As of Tuesday, nearly 77,000 were hospitalised with the virus.

Newly confirmed infections per day in the US have exploded more than 80% over the past two weeks to the highest levels on record, with the daily count running at close to 160,000 on average.

Cases are on the rise in all 50 states. Deaths are averaging more than 1,155 per day, the highest in months.

The out-of-control surge is leading governors and mayors across the US to grudgingly issue mask mandates, limit the size of private and public gatherings ahead of Thanksgiving, ban indoor restaurant dining, close gyms or restrict the hours and capacity of bars, stores and other businesses.

New York City's school system - the nation's largest, with more than 1 million students - suspended in-person classes on Wednesday amid a mounting infection rate, a painful setback in a corner of the country that suffered mightily in the spring but had seemingly beaten back the virus months ago.

Texas is rushing thousands of additional medical staff to overworked hospitals as the number of hospitalised Covid-19 patients statewide accelerates toward 8,000 for the first time since a deadly summer outbreak.

More than 5,400 extra medical personnel have been deployed around Texas by the state alone, said Lara Anton, a spokeswoman for the Texas Department of State Health Services.

The only health care system in the Appalachian mountains of Tennessee and Virginia is warning that it and its workers are stretched so thin that it is only a matter of time before its hospitals will have to turn patients away.

The health system reported having just 16 available ICU beds and about 250 team members in isolation or quarantine. It is trying to recruit hundreds more nurses.

In Idaho, doctors warned that hospitals have almost reached the point where they need to ration care, unable to treat everyone because there are not enough beds or staffers to go around.

"Never in my career did I think we would even contemplate the idea of rationing care in the United States of America," said Dr Jim Souza, chief medical officer for St Luke's Health System.