The first case of the omicron variant in the U.S. has been identified in California, the California and San Francisco Departments of Public Health said.

The CDC said the person traveled from South Africa on Nov. 22.

The individual tested positive on Nov. 29, Dr. Anthony Fauci said at a briefing Wednesday.

The individual, who was fully vaccinated, had mild symptoms that are improving, the CDC said.

"All close contacts have been contacted and have tested negative," the CDC said.

"We knew that it was just a matter of time before the first case of omicron would be detected in the United States," Fauci said.

Fauci cautioned not to read into the mild symptoms of this single case and said the person was fully vaccinated but not boosted.

COVID-19-related hospital admissions in the U.S. are up by 20% since the beginning of November, according to federal data. About one-quarter of the patients are between the ages of 18 and 49.

Nearly 58,000 Americans are in the hospital with COVID-19, including more than 1,300 children, according to federal data.

-ABC News' Arielle Mitropoulos

In South Africa, the National Institute for Communicable Diseases reported 8,561 new COVID-19 cases on Wednesday -- which is nearly double the 4,373 new cases reported on Tuesday.

Seventy-two percent of the new cases were diagnosed in Gauteng province. South African President Cyril Ramaphosa said Sunday that the omicron variant was responsible for most of the infections found in Gauteng over the last two weeks and that the variant is now showing up in all other provinces.

-ABC News' Christine Theodorou

Forecast models used by the CDC -- the COVID-19 Forecast Hub at UMass Amherst -- predict weekly death totals and hospital admissions to increase over the next four weeks.

The model predicts that more than 15,000 Americans will die over the next two weeks, with a total of nearly 810,000 deaths recorded by Christmas.

-ABC News' Arielle Mitropoulos

At least 10 people have tested positive for COVID-19 on a Cruise Norwegian ship disembarking in New Orleans this weekend, according to the Louisiana Department of Health.

Those infected include both passengers and crew members, officials said.

The Norwegian Breakaway departed from New Orleans on Nov. 28 and stopped in Belize, Honduras and Mexico on its voyage. There are more than 3,200 individuals on board, the health department said.

The company required on-site testing in addition to proof of vaccination before boarding the vessel, according to the Port of New Orleans.

The health department said the cruise line has been adhering to appropriate quarantine and isolation protocols. In addition, everyone aboard the ship will be tested for COVID prior to disembarking.

Those who test positive for COVID-19 on the ship will either travel by personal vehicle directly to their private residence or self-isolate according to current Centers fo Disease Control and Prevention guidelines in accommodations provided by Norwegian Cruise Lines.

"The health and safety of our guests, crew and the communities we visit is our highest priority, and we will continue to take all appropriate actions to ensure their wellbeing and protect public health," a Norwegian Cruise Lines spokesperson told ABC News.

"We have identified a handful of COVID-19 cases among guests and crew onboard Norwegian Breakaway, which is scheduled to disembark in New Orleans, LA on December 5. All of the identified cases onboard are asymptomatic. In addition to requiring that 100% of guests and crew are fully vaccinated, per the Company's comprehensive health and safety protocols, we have implemented quarantine, isolation and contact tracing procedures for identified cases."

The spokesperson said the company is testing all individuals prior to disembarkation, and providing post-exposure and quarantine public health guidance by the CDC.

"Any guests who have tested positive for COVID-19 will travel by personal vehicle to their personal residence or self-isolate in accommodations provided by the Company according to CDC guidelines," the spokesperson said. "We take this matter extremely seriously and will continue to work closely with the CDC, the office of Governor John Bel Edwards, the Louisiana Department of Health as well as the city and port of New Orleans. At this time, there have been no changes to scheduled future sailings on Norwegian Breakaway. We will provide additional updates to impacted guests as appropriate."