The California and San Francisco Departments of Public Health have confirmed that a recent case of COVID-19 among an individual in California was caused by the Omicron variant (B.1.1.529). The individual was a traveler who returned from South Africa on November 22, 2021. The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has been since testing positive. All close contacts have been contacted and have tested negative.

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.

On November 26, 2021, the World Health Organization (WHO) classified a new variant, B.1.1.529, as a Variant of Concern and named it Omicron and on November 30, 2021, the United States also classified it as a Variant of Concern. CDC has been actively monitoring and preparing for this variant, and we 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.

“The recent emergence of the Omicron variant (B.1.1.529) further emphasizes the importance of vaccination, boosters, and prevention efforts needed to protect against COVID-19,” said CDC Director, Dr. Rochelle Walensky. “Early data from South Africa suggest increased transmissibility of the Omicron variant, and scientists in the United States and around the world are urgently examining vaccine effectiveness related to this variant. I strongly encourage the 47 million adults who are not yet vaccinated to get vaccinated as soon as possible and to vaccinate the children and teens in their families as well because strong immunity will likely prevent serious illness. I also want to encourage people to get a COVID-19 test if they are sick.”

For more information on the Omicron variant visit https://www.cdc.gov/coronavirus/2019-ncov/variants/index.html.