When the University of Southern California's spring semester begins on Jan. 10, classes will be remote for the first week due to the spread of omicron, university officials said Friday.

In-person classes are set to start Jan. 18.

Students must show a negative test before attending in-person class, and all faculty, staff and students are required to get the booster shot, officials said.

Three of the seven boy banders in K-pop group BTS have tested positive for COVID-19, said their agency, Big Hit Music, according to The Associated Press.

One member, Jin, has a mild fever, while the other two to test positive, RM and Suga, are asymptomatic, the AP said, citing the agency.

Suga and RM tested positive while in quarantine in South Korea following trips to the U.S., the agency said, according to the AP.

The Centers for Disease Control and Prevention has issued an alert to health care professionals across the country to prepare for a possible major surge in infections of COVID-19 due to the high transmissibility of the omicron variant.

Among the CDC's contingency options is shortening the amount of time health care workers must self-isolate following a COVID-19 infection.

Under “conventional” conditions, health care facilities can allow asymptomatic personnel who were infected with COVID-19 to return to work after seven days and a negative test, regardless of vaccination status, according to the new CDC guidance. For health care personnel who were symptomatic, fever should have resolved without medications.

Under “crisis” conditions, health care workers can return to work after five days, if asymptomatic or mildly symptomatic, as a last resort, without testing, the alert states. These health care personnel should wear a respirator or well-fitting face mask, even when they are in non-patient care areas, and facilities should consider assigning them duties that do not include care of immunocompromised patients.

The plan was put into place to mitigate potential staff shortages, according to the CDC.

-ABC News’ Sony Salzman

New York City has seen a fourfold increase in pediatric COVID-19 hospitalizations since early December, according to the New York State Health Department.

The uptick reflects a shift amid the rapid spread of the omicron variant, with the burden of the virus now being borne by young, unvaccinated children.

The increase was observed in children 18 and under beginning the week of Dec. 5 through the current week. During that time, none of the 5- to 11-year-olds admitted to city hospitals with COVID-19 were fully vaccinated, the department said. About one-third of 12- to 17-year-olds admitted due to COVID-19 were fully vaccinated.

"The risks of COVID-19 for children are real,” acting State Health Commissioner Dr. Mary Bassett said in a statement. "We are alerting New Yorkers to this recent striking increase in pediatric COVID-19 admissions so that pediatricians, parents and guardians can take urgent action to protect our youngest New Yorkers."

About 27% of 5- to 11-year-olds and nearly 72% of 12- to 17-year-olds in New York state have received at least one vaccine dose, state data shows.

-ABC News' Sony Salzman and Aaron Katersky