Another Omicron Case is Detected in the US, This Time in a Minnesota Resident

Several more cases of the Omicron variant of the coronavirus were reported in the United States on Thursday, including five people in New York City and on Long Island, officials said. Other cases were reported in Minnesota, Hawaii, California and Colorado.

Gov. Kathy Hochul of New York said one of the cases in her state was a 67-year-old woman from Suffolk County on Long Island who had recently traveled to South Africa and had tested positive for the new variant, which is highly mutated. The woman had been vaccinated and had mild symptoms of Covid-19, Ms. Hochul said. She said the new cases were “no cause for alarm.”

Minnesota health officials said that a man who lives in the state was infected with the Omicron variant after recently traveling to New York City.

A woman who lives in Colorado became the state’s first case of Omicron, state health officials said, after she recently returned from a trip to southern Africa for tourism. She had been fully vaccinated and was eligible for a booster shot but had not yet received it. She was experiencing mild symptoms and isolating at home.

Health authorities had confirmed on Wednesday the first known U.S. case of the Omicron variant was detected in a San Francisco resident who returned to California from South Africa on Nov. 22. And on Thursday, Los Angeles County confirmed an additional case in California, a fully vaccinated adult who had traveled to South Africa in late November.

But an O‘ahu resident with no history of travel is the first Omicron case in Hawaii. “This is a case of community spread,” the state department of health said in a news release. The individual had previously been infected with the coronavirus but was never vaccinated.

Much remains unknown about Omicron, including whether it is more transmissible and capable of causing more serious illness.

According to the Minnesota Department of Health, the man is a resident of Hennepin County, which includes Minneapolis. He had been vaccinated, and he got a booster shot in early November. He is no longer feeling symptoms, the department said.

The man first developed mild symptoms on Nov. 22, shortly after traveling to New York City for the Anime NYC 2021 convention at the Javits Center, the department said. Officials said the man had not been outside the United States recently. Ms. Hochul said on earlier on Thursday that everyone who attended the convention should get tested for the coronavirus, while Mayor Bill de Blasio said the city had activated its contact tracing program to track down people who attended the event. He added that “we should assume there is community spread of the variant in our city.”

One of his close contacts has since tested positive for the coronavirus, officials said, but because a rapid test was used, scientists have not yet determined whether that person, who is also in Minnesota, had the Omicron variant as well.

Genetic sequencing is required to determine which variant a patient has. In recent months the United States has greatly expanded sequencing, but the process takes time — at the Centers for Disease Control, typically about 10 days — to yield results. Currently, according to the agency’s director, Dr. Rochelle P. Walensky, about 14 percent of all positive P.C.R. tests in the U.S. are being sequenced.

Though the new Omicron variant is grabbing headlines, officials warned that the earlier Delta variant of the coronavirus remains prevalent and is still spreading in the United States, posing a grave risk especially to unvaccinated Americans, who are much more likely than vaccinated people to become severely ill if they are infected.