The first case of the omicron variant of COVID-19 has been identified in the U.S., health officials said on Wednesday. The case was detected in a person in California, according to the Centers for Disease Control and Prevention.
"The individual was a traveler who returned from South Africa on November 22," the CDC said in a news release. "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."
Omicron cases have been found in countries from Europe to the Middle East less than a week after the worrying new strain was first reported in South Africa. The U.S. now joins that list, which has grown despite countries' attempts to use travel restrictions to keep the omicron variant outside their borders.
The omicron variant's many mutations โ including 26 to 32 in the protein spike alone โ has led the World Health Organization to say it poses a "very high" risk to global health. While warning that the evidence remains preliminary, the WHO says omicron's mutations "may be associated with immune escape potential and higher transmissibility."
News of the U.S. omicron case in California comes after both President Biden and Dr. Anthony Fauci, the president's chief medical adviser, said they believed it was inevitable for the variant to surface in the U.S. They urged Americans to get vaccinated or get a booster shot, and to be vigilant about wearing masks.
"This variant is a cause for concern โ not a cause for panic," Biden said.
South African officials raised the alarm about the heavily mutated variant, B.1.1.529, on Nov. 24. Two days later, the WHO classified it as a variant of concern and dubbed it omicron.
One week after the alarm was raised, omicron has been identified in at least 23 countries, the World Health Organization said on Wednesday.
On Monday, Rochelle Walensky, director of the Centers for Disease Control and Prevention, issued an update on the public health agency's advice for who should get a COVID-19 vaccine booster.
"Everyone ages 18 and older should get a booster shot either when they are 6 months after their initial Pfizer or Moderna series or 2 months after their initial J&J vaccine," she said in an statement.
This statement replaces earlier guidance that said people ages 18 and older but younger than 50 may receive a booster and others in certain at-risk categories or 50 and older should get a booster.
Walensky said the emergence of the omicron variant "further emphasizes the importance of vaccination, boosters and prevention efforts needed to protect against COVID-19."
The omicron variant's large number of mutations quickly sparked fears that this version of the coronavirus could make COVID-19 spread more easily, and could be more likely to reinfect people who have already had COVID-19.
Researchers are working to learn more about how the omicron variant behaves, particularly whether it's more likely to cause serious illness than other strains.
"It is not yet clear whether Omicron is more transmissible" or if it causes more severe disease, the World Health Organization said on Sunday.
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