Omicron updates: COVID outbreak reported on cruise ship docking in New Orleans

The Los Angeles County Department of Public Health said Thursday evening it has confirmed its first case of the omicron variant.

The county resident had recently traveled to South Africa, returning via London on Nov. 22, and the infection "is most likely travel-related," the department said.

The person is fully vaccinated and their symptoms are improving without medical care, health officials said. Several close contacts have all tested negative.

This is the second confirmed case of omicron in California, following identification Wednesday in a resident of San Francisco who had recently traveled to South Africa.

A new study from South Africa suggests that the new omicron variant might be more likely to lead to COVID-19 reinfection than prior variants, though more research is needed. 

The study, which is not peer-reviewed, found that in November, there was an uptick in the rate of reinfections seen within three months of a primary infection, compared to prior surges driven by the delta and beta variants. 

Researchers, who reviewed records of over 2.7 million people in South Africa with COVID-19 infections in 2020 and 2021, assumed many cases in November were caused by omicron, even though the first cases of the variant were not detected there until late November. 

The vaccination status of individuals with suspected reinfections was unknown in the study, so it is unclear if they had immunity from prior infection or vaccination.  

-ABC News' Dr. John Brownstein, Dr. Esra Demirel and Sony Salzman

Five cases of the new COVID-19 variant omicron have been detected in New York state, Gov. Kathy Hochul announced in a press conference Thursday evening.

Hochul emphasized that battling the delta variant is more of a challenge right now, adding that all five cases have been described as mild.

One case was located in Suffolk County, while three others were in New York City -- two in Queens and one in Brooklyn, Hochul said. A fifth suspected case has also been detected, the governor said, but did not provide details.

-ABC News' Will Gretsky

New York City's latest health mandate will require all nonpublic school employees to be vaccinated by Dec. 20, affecting 56,000 employees of 930 yeshivas, Catholic schools and other private schools.

-ABC News' Aaron Katersky