A person in California has become the first in the U.S. to have an identified case of the omicron variant of COVID-19.

Dr. Anthony Fauci confirmed the variant case during the White House briefing on Tuesday.

In a press release, the CDC said the person, who is fully vaccinated, tested positive after returning to the U.S. from South Africa on Nov. 22.

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

The news comes as scientists continue to study the risks posed by the new strain of the virus.

The Biden administration moved late last month to restrict travel from Southern Africa where the variant was first identified and had been widespread.

Clusters of cases have also been identified in about two dozen other nations, including Hong Kong, Australia, Portugal, and Canada.

Last month, the Biden administration restricted travel from Southern Africa, the Associated Press reported.

The AP reported that the CDC is taking steps to tighten testing rules in the U.S. for those who travel overseas, including requiring travelers to test within a day of boarding a flight to the U.S. regardless of vaccination status.

The World Health Organization (WHO) has classified the omicron strain as a “variant of concern.”

Researchers in South Africa first identified it.