The U.S. has detected the nation’s first case of the omicron variant of the coronavirus in California, the Centers for Disease Control and Prevention (CDC) said Wednesday.
The individual was a fully vaccinated traveler who returned from South Africa on November 22, the CDC said. The person had mild symptoms that are improving, and is self-quarantining.
The person has since tested negative, and all close contacts have also tested negative, the CDC added
The Omicron variant was first identified by South African researchers last week and is believed to have originated in Botswana.
It has 50 mutations, more than 30 of which are on the spike protein, used by the coronavirus to enter and infect cells.
By comparison, the Delta variant – still the predominant variant in the U.S. – has two mutations on the spike protein.
Early evidence suggests it is more transmissible than previous variants but it is unclear if it causes more severe illness or death.
Doctors in South Africa have reported anecdotally that patients infected with Omicron appear to have mild symptoms, such as a dry cough, fever and night sweats, but say they don’t want to draw conclusions just yet.
Genetic analysis of Omicron’s mutations has raised fears that the new variant could be the most dangerous and infectious variety yet.
The U.S. moved on Monday to shut down travel from eight southern African nations including Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa and Zimbabwe.
The Biden administration is weighing stringent new restrictions on international travelers.
But the president sought to offer a voice of calm, as he again told Americans that vaccinations offered the best protection.