SAN FRANCISCO - A person in California became the first in the U.S. to have an identified case of the COVID-19 omicron variant, the White House announced Wednesday as scientists continue to study the risks posed by the new strain of the virus.
The case was detected in San Francisco, Mayor London Breed announced.
The individual, a San Francisco resident, is self-isolating and experiencing mild symptoms, the city health department said in a statement. The person returned from South Africa on November 22 and had been fully vaccinated against COVID, although had not received a booster shot, according to the health department.
Other personal details about the infected traveler, such as age, were not revealed.
"The point is omicron is here. We knew it was here," said Dr. Grant Colfax, the city's director of public health. "We need to get those vaccines and boosters.
"This is cause for concern," Colfax said. "But certainly not a cause for panic."
People who have had close contact with the infected person have tested negative,
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.
"This is the first case of COVID-19 caused by the omicron variant detected in the United States," Dr. Anthony Fauci said at the White House. He said the person was a traveler who returned from South Africa on Nov. 22 and tested positive on Nov. 29.
The Centers for Disease Control and Prevention is taking steps to tighten U.S. testing rules for travelers from overseas, including requiring a test for all travelers within a day of boarding a flight to the U.S. regardless of vaccination status. It was also considering mandating post-arrival testing.
Officials said those measures would only "buy time" for the country to learn more about the new variant and to take appropriate precautions, but that given its transmissibility its arrival in the U.S. was inevitable.
"Even though we don't know that much about this particular variant's impact clinically, it basically proves the point that we need to get immunized. We need to remain vigilant. It also means that something that happens in a distant part of the world, very quickly comes to our part of the world and all over the world," said Dr. Margaret Liu an infectious disease and vaccine expert.
Much remains unknown about the new variant, including whether it is more contagious than previous strains, whether it makes people more seriously ill, and whether it can thwart the vaccine. Fauci, the top U.S. infectious disease expert, said more would be known about the omicron strain in two to four weeks as scientists grow and test lab samples of the virus.
The announcement of the first U.S. case comes before President Joe Biden plans to outline his strategy on Thursday to combat the virus over the winter. Biden has tried to quell alarm over the omicron variant, saying it was a cause for concern but "not a cause for panic."
Biden and public health officials have grown more urgent in their pleas for more Americans to get vaccinated — and for those who have been vaccinated to get booster shots to maximize their protection against the virus.
The Associated Press contributed to this report.