COVID-19 cases have been reported on every cruise ship operating in U.S. waters with passengers, according to the U.S. Centers for Disease Control and Prevention.

More than 90 ships are currently being investigated by the CDC or have been investigated and are still being observed by the agency.

In order to meet the threshold for a CDC investigation, a ship must report COVID-19 cases in more than 0.10% of passengers or have a single crew member test positive in the previous seven days.

The only ships in U.S. waters that have not met this criteria, according to the CDC, only have crew members on board.

-ABC News' Mina Kaji

The Los Angeles County Department of Health updated its COVID-19 safety measures Wednesday and mandated that all of the county's businesses must provide N95 or KN95 masks to employees who work indoors.

"Well-fitting medical grade masks, and surgical masks," are also acceptable under the order.

"Everyone needs to be sensible about how to protect themselves and those they love by layering on protections whenever around non-household members," LA County's health director, Dr. Barbara Ferrer, said in a statement. "At work, this means upgrading your mask if you work indoors and you are in contact with other workers or members of the public."

The Centers for Disease Control and Prevention advisory panel voted Wednesday to approve COVID-19 boosters for 12- to 15-year-olds.

CDC Director Rochelle Walensky will likely to sign off on the move later Wednesday night.

MORE: CDC panel recommends Pfizer boosters for 12-15 year olds, final call expected from CDC director

Shots could go into arms as soon as Thursday morning. The Food and Drug Administration authorized the Pfizer boosters on Monday, paving the way for the CDC’s final green light.

-ABC News' Cheyenne Haslett

The 2022 Grammy Awards have been postponed due to the surge in COVID-19 cases linked to the omicron variant.

"After careful consideration and analysis with city and state officials, health and safety experts, the artist community and our many partners, thx have postponed the 64th Annual GRAMMY Awards Show," CBS and the Recording Academy said in a joint statement.

The statement continued, "The health and safety of those in our music community, the live audience, and the hundreds of people who work tirelessly to produce our show remains our top priority.  Given the uncertainty surrounding the Omicron variant, holding the show on January 31 simply contains too many risks."

A future date for the Grammys has yet to be announced.

The awards show was scheduled to be held at the Arena in Los Angeles and hosted by "The Daily Show's" Trevor Noah.

This is the second year in a row that the Grammys has been postponed. Last year, the show was held in March after its original date was canceled in January.

Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, is standing by her agency's new quarantine and isolation guidance for COVID-19, which the nation’s largest association of physicians has criticized as "confusing."

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. In a scathing statement released Wednesday night, the American Medical Association (AMA) said the new recommendations "are risking further spread of the virus."

"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 AMA's president, Dr. Gerald E. Harmon, said in the statement. "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."

But Walensky defended the new guidance, telling ABC News' Cecelia Vega in an interview Friday on "Good Morning America" that the CDC "make[s] these recommendations in the context of science, in the context of ongoing epidemiology and in the context of what is feasible in collaboration with our public health and local and state public health partners."

"I've read the AMA statement and I have deep respect for the AMA," Walenskey said, "but I will also say we've heard a lot of support for ongoing guidance from public health partners, from other clinical and laboratory partners as well."

Walensky referenced "dozens of studies" that have shown a COVID-19 patient is most infectious in the one to two days before symptoms and the two to three days after symptoms.

"So by five days after your symptoms, the vast majority of your contagiousness is really behind you," she said. "And what we say at day five then is, are your symptoms gone? Are you feeling better? Is your cough gone, sore throat gone? And if so, then it is safe to go out if you are wearing a mask all the time. And that means not going out to restaurants, not going out to gyms, not going out and visiting grandma, but really conscientiously wearing your mask for those last five days."

Walensky noted that people may choose to take an antigen or at-home test at day five, if they have access to one. But it's not required.

"If that test is positive, you should stay home for those extra five days. But if that test is negative you should go out and continue to wear your mask," she said. "You know, these tests are actually not authorized for the purpose of evaluating contagiousness."