Less than a fortnight after Thanksgiving, more than 100,000 Americans lie in overrun hospitals with Covid-19.
In California, around 33 million people are in lockdown under stay-at-home restrictions for at least three weeks including the Christmas holiday, as the state averages 21,000 daily cases.
"We know that those cases that potentially occurred around people's dinner tables, activities, plans, travel through Thanksgiving are going to show up right about now. We're going to be seeing that for many days to come," Dr Mark Ghaly, California's secretary of health and human services, said on Monday.
"We believe that the levels of transmission that we've been reporting so far will likely continue to go up some because of those activities."
New York Governor Andrew Cuomo, who cancelled Thanksgiving plans with his 89-year-old mother after backlash to his own gathering advice, expects hospitalisations to increase further.
Any region in the state where hospitalisation rates don't stabilise after five days will see indoor dining shuttered.
"If you're going to overwhelm the hospital system, then we have no choice but to go to close down," Cuomo said.
He ordered hospitals across the state, treating more than 4600 Covid-19 patients, to increase their 54,000-bed capacity by 25 per cent.
Major Georgia hospitals have turned away patients in ambulances and some have recorded "severe" overcrowding in emergency departments, the Atlanta-Journal Constitution reports.
The United States' top infectious disease expert, Dr Anthony Fauci, said the coronavirus case "blip from Thanksgiving", held on the last Thursday of November, hasn't even arrived yet.
"We're getting those staggering numbers of new cases and hospitalisation before we even feel the full brunt of the Thanksgiving holiday," he told CBS on Monday.
The US has recorded almost 15 million cases of Covid-19 and more than 280,000 deaths.
The total number of deaths in the US reached 283,621 late on Monday, according to Johns Hopkins University, with 1390 fatalities in the previous 24 hours alone. The total number of cases in the country stood at 14,932,613.
CHRISTMAS 'MORE OF A CHALLENGE'
Fauci, a member of the White House coronavirus task force and director of the US National Institute of Allergy and Infectious Diseases, fears his concerns around gatherings in "seemingly innocent settings", travel and being inside with others due to the cold weather "may be even more compounded" at Christmas.
Why is that?
"Because it's a longer holiday," Fauci told CNN.
"With Thanksgiving, it was just the end of the week and then you go back to work the next week. With Christmas, it starts several days before, it goes through Christmas, the week after Christmas into New Year's and the New Year's holiday.
"I think it could be even more of a challenge than what we saw with Thanksgiving. So I hope that people realise that and understand that as difficult as this is, nobody wants to modify – if not essentially shut down – their holiday season.
"We're at a very critical time in this country right now. We've got to not walk away from the facts and the data. This is tough going for all of us."
In advice updated this month, the Centers for Disease Control and Prevention states: "As cases, hospitalisations, and deaths continue to increase across the United States, the safest way to celebrate the winter holidays is to celebrate at home with the people you live with."
For the first time in more than 30 years, Fauci won't be celebrating the holiday season with his daughters.
He plans to mark his 80th birthday, on Christmas Eve, via a Zoom call instead.
Fauci said he doesn't want people "to get despaired" about the "challenging" transition from Thanksgiving to Christmas.
"There is something that we can do about it.
"In the same breath as you say 'These are really, really disturbing numbers', that's not the time to throw our hands up and say 'Well, we're helpless'. We're not.
"There are things that we know, for sure, that we, other countries, various cities and states have done, the fundamental simple things, of the uniform wearing of masks, the physical distancing, the avoiding crowds and congregate settings particularly indoors.
"If we did that across the board, we would be able to blunt the surges we're seeing now."
He said without substantial mitigation of Covid-19, the middle of January could "be a really dark time" for the US.
He added: "We're not helpless … and help is really right around the corner."
Fauci will continue to serve as chief medical adviser on Covid-19 to President-elect Joe Biden beyond inauguration day on January 20.
"I don't want to scare anybody here but understand the facts," Biden said last Thursday.
"We're likely to lose another 250,000 people, dead, between now and January because people aren't paying attention."
Meanwhile, President Donald Trump is expected to sign an executive order on Tuesday to ensure Americans have access to the Covid-19 vaccine before the US helps other nations.
The US government bought 100 million doses of the Pfizer-BioNTech vaccine this year – two doses for 50 million people, in a country with a population of more than 300 million.
The Washington Post reports Pfizer representatives urged Operation Warp Speed to purchase twice as many doses, prior to FDA approval, but the federal officials declined the opportunity.
The pharmaceutical company has reportedly told the Trump administration it will not be able to provide substantial additional doses until late June or July due to deals with other countries.
The world-first rollout of the Pfizer vaccine is due to begin in the United Kingdom on Tuesday, with Health Secretary Matt Hancock volunteering to take it live on television to assuage any doubts over its rapid approval.
The US is expected to grant emergency authorisation for the Moderna and Pfizer vaccines this week, after each reported they were 94.5 to 95 per cent effective against Covid-19 in trials.
"The vaccine's critical," Dr Deborah Birx, the White House coronavirus response co-ordinator, told NBC News.
"But it's not going to save us from this current surge. Only we can save us from this current surge."