By Kaitlan Collins, Jacqueline Howard and Betsy Klein, Dec. 2 (CNN): The United States' first confirmed case of the Omicron coronavirus variant was been identified in California.

In a White House news briefing Wednesday, Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said the case was in an individual who travelled from South Africa on Nov. 22 and tested positive for Covid-19 on Nov. 29.

That individual, Fauci said, is self-quarantining and close contacts have tested negative for the coronavirus so far.

The California and San Francisco public health departments confirmed the case was caused by the Omicron variant through genomic sequencing conducted at the University of California at San Francisco, and the sequence was confirmed by the US Centers for Disease Control and Prevention.

Color Health said in a statement it returned the positive test result through a San Francisco Covid-19 testing program, and Omicron was identified in under 30 hours "from the time of collection to strain confirmation."

Omicron unknowns: The World Health Organization designates Omicron as a "variant of concern." In a technical brief released this week, WHO noted the variant poses a "very high" global risk. The variant was first identified by scientists in South Africa and has since been detected in several countries.

Scientists are working to determine how transmissible the variant is, how sick it makes people and how well current vaccines work against it. Until more information is learned about the variant, the US restricted travel from South Africa and seven other countries.