A medical worker extracts a specimen from a vial with a nasal swab Covid-19 test at the Dignity Health-GoHealth Urgent Care testing site in the international terminal at San Francisco International Airport (SFO) in San Francisco, California, U.S., on Thursday, Dec. 2, 2021. The first confirmed U.S. case of the omicron variant of the coronavirus was detected in California, the Centers for Disease Control and Prevention said, as the recently detected mutation continues its spread around the world. Photographer: David Paul Morris/Bloomberg