The California and San Francisco Departments of Public Health released a joint statement Wednesday announcing the first case of the Omicron variant of COVID-19 detected in the United States. According to the statement, “the University of California, San Francisco identified this case through their sequencing capabilities.”

“California is continuing to monitor the variant’s presence and progress through the state’s robust Whole Genome Sequencing surveillance,” the statement went on to say.

After the joint statement was released, Dr. Anthony Fauci discussed the first Omicron variant cases at White House Press Secretary Jen Psaki’s daily briefing. According to Fauci, the case was detected in a traveler who returned from South Africa on Nov. 22 and tested positive on Nov. 29. Earlier this week, a travel ban on South Africa and seven other nearby countries took effect.

At the briefing Fauci said the traveler was experiencing “mild symptoms.”

“The individual is self-quarantining and all close contacts have been contacted, and all close contacts thus far have tested negative,” Fauci said. “As all of you know, of course, we’ve been discussing this, we knew that it was just a matter of time before the first case of Omicron would be detected in the United States.”

Fauci also said the person was vaccinated but had not received a booster shot. Fauci, as well as White House COVID-⁠19 Response Coordinator Jeff Zients, used the first American Omicron variant case to push all adults to get boosters.

“The President’s medical team continues to believe that existing vaccines will provide some level of protection against severe illness from Omicron, and individuals who have gotten boosters have even stronger protection,” Zients said in a statement. Earlier this month, U.S. health officials approved the use of boosters for all adults, regardless of which company the vaccine came from. On Monday, the Centers for Disease Control and Prevention strengthened their booster recommendation to include all adults.