A coronavirus infection involving the omicron variant has been identified in a Minnesotan who recently traveled to New York.

Genomic sequencing of samples from infected people identified the COVID-19 case, which Minnesota leaders said was inevitable given how quickly the omicron variant spreads.

"This news is concerning, but it is not a surprise," Gov. Tim Walz said. "We know that this virus is highly infectious and moves quickly throughout the world."

The infection involved a vaccinated man from Hennepin County who developed mild symptoms Nov. 22 and sought testing two days later. The man, who has recovered, spoke with state investigators and confirmed he traveled to New York City and attended the Anime NYC convention Nov. 19-21. He received a booster dose of COVID-19 vaccine in early November.

The man stayed in isolation to prevent spreading the infection. A second close contact in Minnesota tested positive for infection as well and is in isolation, but the variant involved in that case had yet to be determined late Thursday.

The first U.S. omicron infection was announced Wednesday in California, but the Minnesota discovery means that the variant was circulating in the country before it was reported Nov. 24 in South Africa. Omicron has been labeled a "variant of concern" because it has spread quickly in South Africa and showed some potential to evade immunity from vaccination or previous infection.

"This case, you know, was getting ill even before we were hearing about omicron," said Kris Ehresmann, infectious disease director for the Minnesota Department of Health.

The presumption is the man was infected during the convention, but that hasn't been confirmed. While the event drew as many as 50,000 people, Ehresmann said the state is aware of a "circle of contacts" of the infected man and is working to determine any with exposure risks who should quarantine.

Minnesota has one of the most aggressive COVID-19 surveillance programs in the country, using a combination of public and private labs to evaluate approximately 20% of all positive specimens for their genomic lineage. Only California and Massachusetts are conducting more genomic sequencing of samples, so state health officials expected that Minnesota would be among the first states to identify an omicron infection.

A missing "S-gene target" is a preliminary warning that omicron is involved, so Minnesota went back and reviewed samples for this indicator, said Sara Vetter, director of the state's public health laboratory. Eight samples were identified with the missing target, including the New York case, she said. Genomic sequencing to identify the variants was completed for five samples but pending for three Thursday afternoon.

Much is unknown about omicron, but state Health Commissioner Jan Malcolm called it a "wake-up call, if we needed another one" to use proven methods of prevention against viral spread. She urged people to continue to seek COVID-19 vaccinations and boosters and to continue existing precautions such as mask-wearing in crowded public places and testing if exposed to the virus.

"The most important thing we can do right now is stay on offense," she said, "and use the tools that we have available to make it as hard as we can for this virus to spread in any form."

Walz surrendered his peacetime emergency powers in a deal with legislators this summer, when COVID-19 cases had declined. Those powers gave him authority to issue mandates on mask-wearing and restrictions on business capacities. Malcolm said a return to those restrictions isn't planned and the existing strategies will work if used voluntarily.

New York Gov. Kathy Hochul said she immediately contacted organizers of the event at the Javits Center after receiving news from Minnesota about the omicron infection. All attendees were vaccinated as a condition of entry to the event and are encouraged to seek testing.

Vaccinated people have had lower rates of severe illness, hospitalization and death, and Hochul said the mild symptoms in the Minnesota case offer some hope to others exposed to the omicron variant.

While early reports indicate that omicron infections aren't resulting in higher rates of severe symptoms, its rapid spread could increase pressure on an overworked health care system, said Dr. John Hick, an HCMC emergency physician who has been involved in Minnesota's COVID-19 response planning.

The rate of omicron-related infection growth in South Africa looks "unprecedented," he said. "So a very rapid spike, even if the disease isn't that severe, is a huge problem."

COVID-19 hospitalizations dipped slightly to 1,549 in Minnesota on Wednesday, but combined with non-COVID patients to occupy more than 96% of available inpatient beds.

A third federal team of 14 medical workers is being dispatched to Minnesota to increase staffing at Southdale Hospital in Edina. The other two teams are in place at HCMC in Minneapolis and St. Cloud Hospital. Hospitals in Colorado, Idaho, Michigan, Montana and New Mexico have received federal staffing support as well amid the current COVID-19 wave that moved north in the fall after taking a severe toll in the South in the summer.

Unvaccinated people continue to make up most of the severe COVID-19 cases in hospitals. Sanford Health on Tuesday reported that 204 of its 227 COVID-19 hospitalizations in Minnesota and the Dakotas involved unvaccinated patients. Of 53 COVID-19 patients on ventilators, 51 were unvaccinated.

Many of the initial omicron infections in South Africa were in younger, healthy college students, so the impact of the variant on a broader population has yet to be determined, said Dr. Ruth Lynfield, state epidemiologist and medical director for the Minnesota Department of Health. "This is early days. I wish we had all of the information now that we will in three weeks."

While the omicron variant has genomic features that suggest it could evade immunity, COVID-19 vaccines likely will still offer protection, just perhaps not the existing 90% level of protection against hospitalization and death, said Matthew Binnicker, vice chair of practice for Mayo Clinic's pathology department. "I don't think it's going to be an impact from 90% to zero. It's going to be a sliding scale."

The state on Thursday reported another 72 COVID-19 deaths and 5,313 infections, raising Minnesota's pandemic totals to 9,554 deaths and 921,249 infections. The deaths mostly involved seniors but included four people in their 40s, a St. Louis County resident in the 35-39 age range and a Steele County resident in the 25-29 age range.

Minnesota also reported a substantial increase in cases involving pre-K-12 students who were infectious while at school. However, that was partly because of a new, faster reporting system that added about 3,400 infections beyond what would have been expected. Even so, more than 2,500 new pre-K-12 infections were reported in each of the first two weeks of November.