The United Kingdom recorded more than 200,000 cases of COVID-19, according to the UK Health Security Agency.

The 218,724 new infections is the highest figure ever reported in a single day and an increase of nearly 60% from the number of cases reported on the same day last week.

However, there has been a backlog of data due to the holiday weekend so the number includes four days of data from Northern Ireland and two days of data from Wales, the UKHSA said.

-ABC News' Mike Trew

Sen. Rob Portman, R-Ohio, tested positive for COVID-19 last night, according to a press release.

Portman took an at-home COVID test which came back positive. The senator said he is asymptomatic and feels fine.

"I have been in contact with the Attending Physician and my personal doctor. I am following their medical advice and following CDC guidelines and isolating for the recommended five days," Portman said in the statement.

He will be working remotely this week, but will not be able to be in Washington, D.C., for votes.

Sweden's King Carl XVI Gustaf and Queen Silvia tested positive for COVID-19 last night, according to a palace statement.

Both are fully vaccinated and have received a third booster shot.

The king and queen said they have mild symptoms and are feeling well, in the statement.

They are isolating at home and contact tracing is ongoing.

More than 1 million new COVID-19 cases were reported in the United States on Monday, according to Johns Hopkins University.

The 1,082,549 new infections were about double last week's record daily cases, according to the university's data. This is likely due to a reporting backlog of cases from holiday testing.

The US recorded 1,688 deaths related to COVID-19 on Monday, below the record high of 4,442, set on Jan. 20, 2021, according to the university's data.

The American Medical Association, the nation’s largest association of physicians, has criticized the Centers for Disease Control and Prevention's new quarantine and isolation guidance for COVID-19, saying the recommendations "are risking further spread of the virus."

The CDC updated its guidelines on Dec. 27, saying asymptomatic people who test positive for COVID-19 should self-isolate for five days rather than 10.

"The American people should be able to count on the Centers for Disease Control and Prevention (CDC) for timely, accurate, clear guidance to protect themselves, their loved ones, and their communities. Instead, the new recommendations on quarantine and isolation are not only confusing, but are risking further spread of the virus," the American Medical Association's president, Dr. Gerald E. Harmon, said in a statement Wednesday night.

Harmon referenced data cited by the CDC in its rationale for shortening the isolation period, which estimates 31% of people remain infectious five days after a positive COVID-19 test, suggesting that data proves thousands of Americans could return to their lives while still infected.

"With hundreds of thousands of new cases daily and more than a million positive reported cases on January 3, tens of thousands -- potentially hundreds of thousands of people -- could return to work and school infectious if they follow the CDC’s new guidance on ending isolation after five days without a negative test," Harmon said. "Physicians are concerned that these recommendations put our patients at risk and could further overwhelm our health care system."

Harmon said a negative COVID-19 test should be required for ending isolation after a positive test, as reentering society without knowing whether an individual is still positive ultimately risks further transmission of the virus.

Although test availability remains an issue nationwide, Harmon also called on the Biden administration to ramp up production and distribution of tests, adding that "a dearth of tests at the moment does not justify omitting a testing requirement to exit a now shortened isolation."

-ABC News' Arielle Mitropoulos