(CNN)On a day the United States registered another record for Covid-19 patients in hospitals, the country passed 21 million cases of the coronavirus, according to Johns Hopkins University.
The US, with 21,007,694 cases as of Tuesday evening, has almost as many as the next three nations -- India, Brazil and Russia -- have combined.
The US has added 1 million cases in the past four days.
That's as the record number of hospital patients Tuesday topped 131,200, according to the Covid Tracking Project.
And some states are warning the worst may be ahead. Experts have said holiday travel and gatherings could help fuel another surge of Covid-19 infections.
In California, officials say ICU units in at least two regions are filled to practical capacity. And because of resource limitations, Los Angeles County ambulance crews have been instructed not to transport any patient in blunt traumatic or nontraumatic cardiac arrest if they can't first be resuscitated in the field.
Some EMTs have had to wait with patients outside hospitals for hours because the facilities don't immediately have space to take the patients in.
"This is a humanitarian catastrophe now unfolding in Los Angeles, and I worry it won't stop in Los Angeles. We'll be looking at this in other metro areas as well," Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, told CNN on Tuesday.
"We are heading into what we anticipate as a surge on top of a surge," Gov. Gavin Newsom said Monday. "It's going to put a lot of pressure on hospitals, and I see it coming out of the holidays."
Mississippi Gov. Tate Reeves said the state had "more patients with Covid in ICU beds at the end of last week than we have had at any other period throughout this pandemic."
And he expects "some very large numbers with the spread from the holiday gatherings combined with the backlog and testing and reporting that may have occurred during the last 10 days."
Weeks ago, Los Angeles officials said part of the brutal surge in infections and hospitalized patients they were seeing was due to Thanksgiving gatherings. Now, they asked residents to do their part to avoid even higher numbers.
"If we fail to use the tools currently available, our frontline health care workers, now caring for distressingly large numbers of Covid-19 patients, will face many more weeks of increasing numbers of patients and the heartbreaking loss of many lives," Los Angeles County Public Health Director Barbara Ferrer said Monday.
Dr. Thomas Yadegar walks Sunday in a temporary emergency room built into a parking garage at Providence Cedars-Sinai Tarzana Medical Center in Tarzana, California.
Nationwide, daily death reports are at near-record levels:
The US has averaged 2,663 coronavirus deaths a day over the last week -- about one death every 32 seconds -- according to JHU data.
That's just below the peak daily average of 2,715 reached on December 22.
Georgia is fifth state with UK coronavirus variant
The first case of the UK coronavirus variant in Georgia has been identified, according to a release from the Department of Public Health.
The variant was discovered during analysis of a sample sent by a pharmacy in Georgia to a commercial lab, the release said.
The resident is an 18-year-old man with no travel history. He is isolating at home.
Four other states -- California, Colorado, Florida and New York -- have confirmed cases of the variant, which health experts say is more transmissible than most other strains. San Diego County announced 24 more cases and four probable cases.
"The 24 newly confirmed patients are believed to have no travel history and to have come from 19 different households, but the investigation and contact tracing are ongoing," health officials said in a statement. Four are younger than 10 years old.
The variant was found in southern England in September and health officials believe it is already in many states but the US doesn't do the same amount of genome sequencing tests that find the variant as other countries.
4.8 million vaccine doses administered
Vaccinations, meanwhile, are ongoing, but experts have said it likely will take a couple months before they are widespread enough to make any meaningful impact.
About 17 million doses had been distributed and 4.8 million had been administered, according to Centers for Disease Control and Prevention figures updated Tuesday morning.
Only four states have so far administered at least half of the vaccine doses that have been distributed to them, according to the CDC data: Connecticut, North Dakota, South Dakota and Tennessee.
While some states have acknowledged on-the-ground issues that have contributed to delayed vaccinations, many have for months said they needed significantly more federal funding to be able to execute vaccine-rollout plans.
The CDC advised giving the first rounds of vaccinations to health care workers and residents of long-term care facilities, followed by adults ages 75 and older and "frontline essential workers." But states are free to make their own decisions on priority.
In Florida, where vaccines are open to anyone 65 and older, each county health department decides how to administer the shots. In some places, county hotlines have been overburdened and vaccination sites have featured hourslong wait times.
In Daytona Beach, seniors lined up early Tuesday in their vehicles for a chance to get one of 1,000 shots at Daytona Stadium. Gates opened at 7 p.m. Monday, so that people could wait overnight for the 9 a.m. Tuesday start.
Capacity was reached more than two hours before the event's start, and others were turned away, city officials said.
"We're going to need to start opening up (more) outdoor arenas and stadiums and having (them) staffed with qualified people," to get vaccinations rolling properly, Hotez said. "It's going to take federal support money and logistics."
Dr. Anthony Fauci said Tuesday he believed the vaccine rollout will pick up momentum" in the coming weeks.
"The government and the locals, including the governors and the mayors and others, have just started in the last couple of weeks in December, right in the middle of the holiday season," Fauci, director of the National Institute of Allergy and Infectious Diseases, told Newsday's Randi Marshall during a virtual event.
"I think we should wait until the first and second week in January to see if we can catch up with the pace," he said.
The federal government's Operation Warp Speed said it distributed more than 3 million coronavirus vaccines Tuesday.
New York Gov. Andrew Cuomo doubled down on previous comments that some hospitals in the state are not administering their vaccine allocations fast enough, and said that going forward the state will distribute vaccines to hospitals that "do a better job."
"In the meantime, for those hospitals that already have the allocation: get it out, get it out, get it out," Cuomo said.
NYC Health + Hospitals CEO Mitch Katz said earlier Tuesday that the vaccine administration percentages announced by the governor's office were not a fair representation of what the health system is undertaking.
Covid-19 likely 3rd leading US cause of death in 2020
Covid-19 was likely the third leading cause of death in the United States in 2020, according to statisticians at the CDC.
The agency only has early data on the leading causes of death for last year, and researchers are still combing through those numbers. But provisional data suggest that Covid-19 may have caused enough deaths in 2020 to rank third, CDC statisticians told CNN in an email.
"We still only have provisional data through December 26. We should be getting more data in very soon," statisticians said via email. "To that point we estimate there were between 316,252 and 431,792 excess deaths in 2020. Our provisional death certificate data through that point show over 301,000 deaths involving Covid-19, which would likely place it third among leading causes of death."
They added that "there is enough distance" between the numbers of death caused by cancer, the second leading cause in 2019, and those caused by accidents or unintentional injuries, the fourth leading cause in 2019, "to be comfortable saying" that Covid-19 was the third leading cause for 2020.
As of Tuesday night, more than 357,000 people had died of Covid-19 in the US since the pandemic began, according to Johns Hopkins University's count.
