The individual was a traveler who returned from South Africa on Nov. 22, according to the U.S. CDC.

NEW YORK, Dec. 1 (Xinhua) -- The United States has identified the country's first confirmed case of the Omicron COVID-19 variant in the state of California, health authorities said Wednesday.

The California and San Francisco Departments of Public Health have confirmed that a recent case of COVID-19 among an individual in California was caused by the Omicron variant. The individual was a traveler who returned from South Africa on Nov. 22, the U.S. Centers for Disease Control and Prevention (CDC) said in a news release.

Officials said that genomic sequencing was conducted at the University of California, San Francisco and the sequence was confirmed at CDC as being consistent with the Omicron variant, which was first detected in southern Africa last month.

The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has since tested positive. All close contacts have been contacted and have tested negative, according to the CDC.

The health agency said the emergence of the variant "emphasizes the importance of vaccination, boosters, and general prevention strategies needed to protect against COVID-19. Everyone 5 and older should get vaccinated. Boosters are recommended for everyone 18 years and older."

South Africa reported the variant to the World Health Organization last week, and the agency labeled Omicron a "variant of concern." The Joe Biden administration responded by announcing international travel restrictions for eight southern African countries.