NEW YORK (REUTERS) - The number of patients hospitalised with Covid-19 in the United States has jumped nearly 50 per cent in the last two weeks, forcing states to impose new restrictions to curb the alarming viral spread as Americans face a potentially grim winter and holiday season.

Nearly 79,000 people were being treated for the disease in hospitals across the country on Thursday, a Reuters tally showed, the most at any time during the pandemic.

The country has been recording 161,607 new cases daily on a seven-day rolling average as of Wednesday.

The acceleration has forced a spate of new school and business closings to slow community spread, upending lives of Americans once again.

Suzanna Riordan, a Brooklyn mother, said she burst into tears upon hearing the announcement that New York City public school classrooms would shut beginning on Thursday as the city's seven-day positive test rate average hit a previously-agreed closure threshold of 3 per cent.

Riordan's daughter Olivia, seven, had been excited at the prospect of adding one more day of in-person education a week starting next week as part of the city's hybrid learning plan, Riordan said.

"Since September, she's gotten maybe seven days in school," Riordan said.

"And those are the days where... she comes home excited and happy and she gets to see other second graders. And that's gone again."

New York City Mayor Bill de Blasio defended his decision to revert to at-home virtual schooling, adding that additional safety standards to reopen the largest US school district would be announced before next Thursday's Thanksgiving holiday.

"The schools have been shut temporarily but only temporarily. They will back be and they'll be safer than ever,"de Blasio told reporters.

The mayor also said he expected the state would shut down indoor dining and gyms in his city within "a week or two" given the current rate of infections.

Stringent measures were going into effect across the country this week as the US Covid-19 death toll passed a quarter million, the highest in the world.

Michigan began a three-week shutdown on Wednesday that closed gyms, high schools, colleges and entertainment venues.

Minnesota, one of several Midwest states dogged by soaring infection rates per capita, ordered a shutdown of restaurants, bars, fitness centers and entertainment venues starting on Friday through at least Dec 18. More than 90 per cent of hospital intensive care unit (ICU) beds were already occupied in the eastern half of the state.

In the nation's capital, the Smithsonian Institution announced it would close its museums and the National Zoo beginning on Monday, with no set reopening date.

Meanwhile, the Trump administration has persisted in criticising state efforts to curb the virus by shutting down parts of their economies.

He has also refused to share critical Covid-19 data with President-elect Joe Biden and his transition team, threatening to slow the incoming administration's pandemic response.

The soaring rate of infections and shutdowns aimed at reversing that trend portends a bleak winter for the American economy.

Last week, the number of Americans filing new claims for jobless benefits unexpectedly rose as new business closures unleashed a fresh wave of layoffs and further slowed the labour market recovery.

Initial claims for state unemployment benefits totalled a seasonally adjusted 742,000 for the week ended Nov 14, compared to 711,000 in the prior week, the Labour Department said on Thursday. Economists polled by Reuters had forecast 707,000 applications in the latest week.

Limit holiday gatherings

Health and government officials have warned that the sharp rise in hospitalisations could worsen if Americans do not limit their Thanksgiving holiday celebrations to small, single-household gatherings.

The US Centres for Disease Control and Prevention issued a "strong recommendation" on Thursday that Americans refrain from travelling for the holiday.

The Northeast, which for months had successfully held the virus at bay after the pandemic's crushing first wave in the spring, has experienced the highest percentage jump in hospitalisations at 85.4 per cent over the past 14 days, according to Reuters data. During that same period, hospitalisations in the Midwest have risen by 56.8 per cent, in the West by 50.1 per cent, and in the South by 34.4 per cent.

In Maryland, which reported a record 2,910 new cases in a 24-hour period on Thursday, the Baltimore public school district said it would halt in-person learning the week after Thanksgiving to avoid exacerbating virus spread that may occur over the holiday.

Looking further ahead, officials in Pennsylvania announced that crowds will not be permitted to attend annual Groundhog Day festivities in Punxsutawney.

Famous furry prognosticator, Punxsutawney Phil, will still come out on Feb 2 to predict when winter will end, but the event will be streamed online, the Punxsutawney Groundhog Club's website said.