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

British Prime Minister Boris Johnson apologized Wednesday for attending a party during England's strict lockdown in 2020.

It was the first time that Johnson acknowledged he went to a garden party at his official residence and office on London's Downing Street in May 2020. He is facing growing anger and calls for his resignation over claims he and his staff flouted COVID-19 restrictions by holding a "bring your own booze" party. At the time, Johnson's government had imposed restrictions barring people in England from meeting more than one individual outside their household.

During the weekly Prime Minister’s Questions session in the House of Commons in London on Wednesday, Johnson said he had considered the garden party to be a work event to thank his staff for their efforts during the pandemic.

"I want to apologize," Johnson told lawmakers. "With hindsight, I should have sent everyone back inside."

The prime minister urged people to await "the full conclusion" of an investigation by senior civil servant Sue Gray into several alleged parties by government staff. Gray will report her findings by the end of the month.

Opposition Labour Party leader Keir Starmer said Johnson's defense was "the pathetic spectacle of a man who has run out of road" and demanded he "do the decent thing and resign."

The prime minister declined to resign and didn't explicitly admit that he had broken any rules, but said he understood "the rage."

"I know that millions of people across this country have made extraordinary sacrifices over the past 18 months," he added. "I understand the anger, the rage that they feel at the thought that people in Downing Street were not following those rules."

-ABC News' Guy Davies, Ian Pannell and Joseph Simonetti