A recent case of COVID-19 in an individual in California was caused by the omicron variant, the California and San Francisco departments of public health confirmed Wednesday.
The Centers for Disease Control and Prevention (CDC) said the individual had traveled to South Africa and returned on Nov. 22.
The unnamed person, who was fully vaccinated, has since tested positive and is now self-quarantining with mild symptoms that are improving, the CDC said. All close contacts have been contacted and have tested negative.
Agency officials said genomic sequencing was conducted at the University of California, San Francisco and the sequence was confirmed at CDC as being consistent with the omicron variant.
“This will be the first confirmed case of COVID-19 caused by the omicron variant detected in the United States,” CDC officials said in a statement.
On Nov. 26, the World Health Organization (WHO) classified the omicron strain as a “variant of concern,” as U.S. officials four days later.
The CDC said it has been actively monitoring and preparing for the variant and will continue to work diligently with other U.S. and global public health and industry partners to learn more.
“Despite the detection of omicron, delta remains the predominant strain in the United States,” CDC officials said. “The recent emergence of the omicron variant (B.1.1.529) further emphasizes the importance of vaccination, boosters, and general prevention strategies needed to protect against COVID-19. Everyone 5 and older should get vaccinated boosters are recommended for everyone 18 years and older.”