Ten states -- all of which have colder temperatures -- have seen upticks in hospital admissions in recent weeks, according to federal data: Alaska, Colorado, Maine, Michigan, Minnesota, New Hampshire, North Dakota, Pennsylvania, Vermont and Wyoming.

However, nationwide, just under 58,000 Americans remain hospitalized, a major drop from 104,000 patients at the end of the summer, according to federal data.

Death rates remain high, with more than 1,000 Americans dying each day, according to federal data.

Over the last month, the U.S. has reported approximately 45,000 COVID-19 deaths, including nearly 7,600 deaths in the last week.

-ABC News' Arielle Mitropoulos

The United Kingdom recorded 233 COVID-19 deaths in the last 24 hours, the highest total since March 5, according to government data.

In a statement confirmed by ABC News, issued before the new figures were published, the prime minister’s office said it was keeping a "very close eye" on the numbers and urged people to get their booster shots.

"We have seen case rates rising, we've started to see some indications that hospitalisations and death rates are increasing also," a spokesman for the prime minister said. "It's important that the public understand that getting your booster jab is just as important as getting your first and second dose."

-ABC News' Guy Davies

A national state of emergency for children's mental health has been declared by the American Academy of Pediatrics, the American Academy of Child and Adolescent Psychiatry and the Children’s Hospital Association.

"The COVID-19 pandemic has taken a serious toll on children's mental health as young people continue to face physical isolation, ongoing uncertainty, fear and grief," the groups said in a statement Tuesday. "Even before the pandemic, mental health challenges facing children were of great concern, and COVID-19 has only exacerbated them."

Mental health ER visits jumped 24% for kids ages 5 to 11 between March and October 2020, the groups said. Mental health ER visits skyrocketed 31% for kids ages 12 to 17.

From early 2019 to early 2021, there was a more than 50% jump in ER visits for suspected suicide attempts for girls ages 12 to 17, they said.

More than 140,000 kids in the U.S. have lost a primary or secondary caregiver during the pandemic, the organizations added.

-ABC News' Anne Flaherty

The U.S. Food and Drug Administration is considering allowing Americans to receive a booster shots from a different brand than their original shots, a source familiar with the agency’s planning told ABC News Monday.

The New York Times first reported the proposal Monday evening.

The FDA is moving toward recommending people get boosters that match their original doses -- from the Pfizer or Moderna or Johnson & Johnson -- but the agency may also allow health care providers to give certain patients boosters that do not match their initial doses, the source said.

An advisory committee of the Centers for Disease Control and Prevention is slated to discuss boosters this week and could issue recommendations for boosters by the end of the week.

-ABC News' Eric Strauss