The acting head of the Food and Drug Administration warned Tuesday that most people in the United States will contract COVID-19, as the country grapples with record levels of infections and hospitalizations.

"I think it's hard to process what's actually happening right now, which is most people are going to get COVID," Dr. Janet Woodcock, the acting commissioner of the FDA, said while testifying before the Senate Committee on Health, Education, Labor and Pensions on Capitol Hill in Washington, D.C. "What we need to do is make sure the hospitals can still function, [and] transportation, you know, other essential services are not disrupted while this happens."

New COVID-19 cases increased 55% worldwide in the week ending Jan. 9, the World Health Organization said on Tuesday.

More than 15 million new cases were reported, up from the about 9.5 million in the previous week, the United Nation's health agency said in its weekly epidemiological update. Omicron is "rapidly replacing" other variants of the virus, according to the update.

"In terms of disease severity, there is growing evidence that the Omicron variant is less severe as compared to other variants," the WHO said.

Last week's increase marked a slowdown from the 71% spike reported the previous week, following a "gradual" rise since October, according to the update.

Reported cases in the Americas increased 78%, down from a 100% increase the week prior. The greatest increase in new cases came in Southeast Asia, where newly reported cases increased 418%, the WHO said.

On average, the U.S. is now reporting more than 750,000 new COVID-19 cases per day, a more than sixfold increase compared to one month ago, according to federal data.

On Monday, the U.S. recorded a single-day high of more than 1.4 million new cases, following soaring demand for tests and a backlog of weekend reporting data.

The surging national case numbers may not be indicative of what is happening in every region of the country and the overall increase in the U.S. does not necessarily mean that some regions will not see a plateau or decline in numbers.

Although the incredibly high case totals are most certainly due, in large part, to the country's latest omicron surge, the data is incredibly volatile on a day-to-day level. Many states no longer report data over the weekends, which can create an illusion of very low totals on weekends and very high daily numbers on Mondays and Tuesdays.

Also, there was a major surge in demand over the holidays, which could artificially increase numbers. However, experts say overall totals are likely undercounted given the increased use of at-home COVID-19 testing.

-ABC News' Arielle Mitropoulos

In Los Angeles, the hard-hit Providence Cedars-Sinai Tarzana Medical Center is "in complete disaster mode," Dr. Eric Snyder, medical director of the emergency department, told ABC News.

The emergency room is overflowing, with 22 patients currently waiting for beds.

"These are patients who’ve been accepted by a doctor, but have no place to go," he said.

Snyder said the hospital is in far worse shape than at any point in the pandemic. Tents have been set up behind the hospital and a doctor is going patient to patient, hoping to send those home who don't need hospital care, he said.

“We are 100% broken," Snyder said.

-ABC News' Matt Gutman

About 3,000 United Airlines workers currently have COVID-19, though none are in the hospital, the airline said.

On one recent day, one-third of all United Airlines employees at Newark Airport called in sick, the airline said.

United CEO Scott Kirby said the airline is cutting its near-term flight schedule to ensure they have enough staffing.

Kirby added that, prior to the vaccine requirement, United had one employee die each week from COVID-19.

-ABC News' Sam Sweeney