The CDC issued a statement that the California and San Francisco Departments of Public Health confirmed the case in a traveler who returned from South Africa on Nov. 22.
“The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has been since testing positive,” the statement read.
The variant, which was first detected in southern Africa last week, has a high number of mutations that suggest it may spread just as or more easily than the delta variant, which currently accounts for 99.9% of COVID-19 cases in the U.S.
Still, scientists have cautioned that it’s still unclear whether omicron is more dangerous than other versions of the virus that has killed more than 5 million people worldwide. It is also unknown how well our vaccines and treatments would work against the variant.
The World Health Organization said Monday that the global risk of the new variant is “very high.”
“Omicron’s very emergence is another reminder that although many of us might think we’re done with COVID-19, it’s not done with us,” Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, told a special session of the World Health Assembly.
The U.S. last week restricted travel from South Africa and seven neighboring countries. The CDC has also announced that anyone traveling from those areas will be required to provide their names and contact information while they remain in the U.S.
The variant has been detected in the U.K., the Netherlands, Italy, Portugal, Germany, Belgium, Canada, Australia, Israel and Hong Kong, among other countries.
While world leaders and health experts are urging people to get vaccinated as soon as possible, some countries are struggling to inoculate their populations due to lack of access.
This story was originally published on NBC News.