The United States surpassed its record for covid-19 hospitalizations on Tuesday, with no end in sight to skyrocketing case loads, falling staff levels and the struggles of a medical system trying to provide care amid an unprecedented surge of the coronavirus.

Tuesday’s total of 145,982 people in U.S. hospitals with covid-19, which includes 4,462 children, passed the record of 142,273 set on Jan. 14, 2021, during the previous peak of the pandemic in this country.

But the highly transmissible omicron variant threatens to obliterate that benchmark. If models of omicron’s spread prove accurate — even the researchers who produce them admit forecasts are difficult during a pandemic — current numbers may seem small in just a few weeks. Disease modelers are predicting total hospitalizations in the 275,000 to 300,000 range when the peak is reached, probably later this month.

As of Monday, Colorado, Oregon, Louisiana, Maryland and Virginia had declared public health emergencies or authorized crisis standards of care, which allow hospitals and ambulances to restrict treatment when they cannot meet demand.

Nurses and other hospital staff continued to fall sick themselves, raising patient-to-nurse ratios in some places to high levels.

“Our systems and personnel are under extreme strain and I’m not sure how long we can sustain it,” Russell Buhr, a pulmonary and critical care physician at Ronald Reagan UCLA Medical Center in Los Angeles, said in an email.

The omicron variant of the virus still appears to cause less severe illness and fewer deaths, and vaccines and boosters are holding up as bulwarks against both. But the sheer number of cases among unvaccinated people, as well as breakthrough cases, was putting pressure on intensive care units and hospital covid wards anyway, even as fewer people are in the ICU than during last January’s peak. Throughout the pandemic, deaths have also lagged behind jumps in the number of infections by a few weeks. Those numbers may rise as well in days to come.

As of Monday there were 23,524 covid patients in ICUs nationwide, compared with a record 29,591 on Jan. 12, 2021. About 1,200 hospitals — just under a quarter — reported a critical staffing shortage this week, and another 120 reported anticipating a staffing crisis within a week, according to data kept by the U.S. Department of Health and Human Services.

The West is experiencing dire shortages, with 29 percent of hospitals experiencing a crisis and 32 expecting one this week. The worst-hit states are Vermont and Rhode Island, where more than 60 percent of the hospitals anticipate staffing crises this week.

The latest coronavirus variant has taken over as the dominant strain in the U.S. Here’s what we know about omicron. (Monica Rodman, Sarah Hashemi/The Washington Post)

In California, 38 percent of hospitals are in crisis, and 43 percent expect a crisis this week. The state Department of Public Health on Sunday began allowing health-care workers with asymptomatic covid cases to return to work immediately without isolating. Those who are exposed and asymptomatic need not test or quarantine.

Under the temporary guidelines, hospitals must first try to bring in contract staff and consider changes to nonessential procedures, and infected staff must wear N95 masks. State officials cited “the critical staffing shortages currently being experienced across the health-care continuum because of the rise in the Omicron variant” in making the change.

Sandy Reding, a nurse and president of the California Nurses Association, said that when the new rules were issued, “I had to read it again.”

“That they would implement such a process is absurd,” she said. “To put an infusion of covid positive employees into that workforce, we’re going to see some devastating impacts.”

Jeremy Faust, an emergency room physician at Brigham and Women’s Hospital in Boston, compiles county-level data that he said shows hospital overcrowding is worse than it appears in some parts of the country. He said the danger of rising ratios of patients to health-care providers is situational.

“A team that is used to carrying 8 patients at once can probably safely expand to ten,” Faust wrote in an email. “But if the complexity of care means that the team is usually capped at 4 or 5 patients, ten could become a challenge and pose new risks.”

Delaware’s largest health system, ChristianaCare, announced Monday that it was activating crisis standards of care. In the days leading up to Christmas, hospital leaders warned they were over capacity, suspending elective surgeries and treating some patients in hallways. In a statement announcing the rationing, the health system said about four in 10 patients across three hospitals are infected with the virus.

“There’s nothing mild about omicron. It’s overrunning our hospital, and it’s outstripping our ability to provide care such that we have to alter our standards,” said Kenneth Silverstein, the system’s chief physician executive, in an interview. “We are seeing sick patients, and we are seeing a lot of them. While the absolute percentage of patients requiring ICU treatment being admitted may be lower, the total number of ICU patients is greater.”

Under Colorado’s crisis standards of care, emergency crews were told to consider not transporting to hospitals patients younger than 60 who are not showing severe symptoms and who do not have a high-risk medical history.

Oregon’s interim crisis guidelines, released Friday, call for hospitals coping with overwhelming patient demand to establish triage teams to score each patient based on likelihood of survival with treatment, rather than age or quality of life.

At University Hospital in Newark, about 61 percent of covid patients did not have coronavirus as their primary diagnosis, meaning that they arrived seeking care for another reason but tested positive when checked for coronavirus.

The Los Angeles County Department of Health Services, which runs four public hospitals, reported last week that about two-thirds of its 150 covid patients were incidental cases, up from about 20 percent in last winter’s peak.

As the world enters a third year of the coronavirus pandemic, people wonder when and how it will end. History offers important lessons. (Joy Yi/The Washington Post)

Overall the daily average of new infections stood at more than 714,600 Monday, according to data tracked by The Washington Post, up 74 percent from a week ago. The daily average of new deaths was 1,674, up 6 percent from a week earlier.

More than 23,000 covid patients were in intensive care, making up just over a third of all intensive care patients, according to the latest HHS report. That’s the highest share of intensive care patients with covid since the peak of the delta surge in September.

Covid patients are staying longer in the hospital than at any time since July 2020, the data show, averaging more than 20 days each. The longer stays indicate that patients are sicker and putting greater stress on the medical system.

Late Sunday, the Institute for Health Metrics and Evaluation at the University of Washington predicted that hospitalizations would peak at 273,000 on Jan. 25, with reported infections rising to 1.2 million a day by Jan. 19.

Jeffrey Shaman, an infectious-disease modeler and epidemiologist at Columbia University, predicted that covid hospitalizations may reach 300,000 to 350,000 about Jan. 27.

Dan Diamond and Jacqueline Dupree contributed to this report.