South African health officials announced another day of increases in COVID-19 cases.

The country recorded 11,125 new confirmed cases, Sunday, which represented a 23.8% positivity rate increase, according to South Africa's National Institute for Communicable Diseases (NICD).

About 71% of these new cases were diagnosed in Gauteng province where 28 new hospitalizations were recorded Sunday, according to statements from the provincial authority. More than 1,539 people are receiving hospital treatment in the province, the provincial authority said.

South Africa has detected and confirmed 228 omicron variant cases as of Sunday afternoon, data from the GISAID variant tracker showed.

Africa's Centers for Disease Control and Prevention said roughly 24% of South Africa's population is fully vaccinated as of Sunday afternoon.

-ABC News' Christine Theodorou and Liezl Thom

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."

All international travelers to the UK ages 12 and up must show proof of a negative COVID-19 test taken within two days of departure, officials announced Saturday.

The changes go into effect at 4 a.m. Tuesday and apply to all travelers, regardless of vaccination status, coming from countries that are not on the "red list," according to Health Secretary Sajid Javid.

Previously, travelers to the UK did not have to take a COVID-19 test if they were fully vaccinated and had not been in a red list country.

UK officials also announced that Nigeria will be added to the red list, effective 4 a.m. Monday.

The changes are to "slow the incursion of the Omicron variant," Javid said on Twitter.

Over 97% of Centers for Disease Control and Prevention employees are vaccinated, according to data released Friday by the Department of Health and Human Services.

Additionally, 99% of the agency's employees are "in compliance," meaning they have either initiated vaccination or have submitted a request for a medical or religious exemption.

In other HHS divisions, 96% of Food and Drug Administration employees are vaccinated and 99% are in compliance. At the National Institutes of Health, 97% are vaccinated and 99% are in compliance.

The data release comes as some Republican senators have pushed CDC Director Rochelle Walensky for vaccination rates at her own agency as she defends Biden's federal workers vaccine mandate, which is being challenged in federal court.

-ABC News' Cheyenne Haslett

With several cases of the omicron variant confirmed in the United States, officials have learned that "many" of those infected are vaccinated against COVID-19, according to Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention.

But many of the patients experiencing mild symptoms from omicron are also vaccinated, Walensky said, indicating that the current COVID-19 vaccines are fending off severe disease.

"We've seen omicron in about five states now and we're continuing to do investigations in other states as probable cases emerge. But what we can say, based on what these cases are showing -- some have mild disease, some may have more severe disease, many of them are vaccinated -- and what we're seeing now is that many of the people with mild disease were the vaccinated people," Walensky told ABC News' Cecelia Vega in an interview Friday on "Good Morning America."

"So we still have a lot of science to do to understand how these vaccines are working against omicron, except to say that we know for every variant that we've had it's better to be vaccinated than unvaccinated," she added.

Walensky emphasized that, despite the global frenzy around omicron, delta remains the dominant variant in the U.S.

"We have 90,000 new cases of COVID-19 every day and about 99.9% of them continue to be delta," she said. "So we can't lose sight of the fact that the vast majority of what we have here in the United States is delta, and we know how to tackle delta with vaccines, with boosters, with masking and all of our prevention measures we have been using all along."

Walensky acknowledged that there are still many unknowns about omicron, including the severity of disease, transmissibility and vaccine effectiveness.

"I think we really do need to follow the science here and understand how our vaccines are going to work against omicron," she said. "It may very well be that our vaccines actually work quite well and continue to work quite well against severe disease, and those are the studies that are ongoing."

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CDC director talks concerns over omicron variant in US