The Minnesota Department of Health said Thursday that lab testing had confirmed the state’s first omicron COVID-19 case.

The news comes a day after U.S. officials announced that the nation's first case of the variant had been confirmed in a resident of San Francisco, California, who had recently returned to the Bay Area from South Africa.

The infected Minnesota resident had returned to the Gopher State from domestic travel and the variant had been detected through a variant surveillance program, the agency said.

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The individual is an adult male and a resident of Hennepin County. He was vaccinated against COVID-19.

The man developed mild symptoms on Nov. 22 and sought COVID-19 testing on Nov. 24. Those symptoms have since resolved.

"The Minnesota Department of Health (MDH) today announced that its Public Health Laboratory has found the variant of the SARS-CoV-2 virus known as Omicron in a specimen from a Minnesota resident with recent travel history to New York City," the department wrote.

The man told investigators that he had attended the Anime NYC 2021 convention at New York City's Javits Center from Nov. 19-21.

He was advised to isolate himself from others.

"Since the beginning of this pandemic, Minnesota’s nation-leading genome sequencing infrastructure and strong testing network have allowed the state to quickly track the COVID-19 virus and better understand its spread," Gov. Tim Walz said in a statement. "Today, those tools detected a case of the Omicron variant in Minnesota. This news is concerning, but it is not a surprise."

Minnesota Commissioner of Health Jan Malcolm said the finding underscores the importance of continued efforts by Minnesotans to limit the spread of COVID-19 in any form.

"We still have more to learn about Omicron, but the most important thing we can do right now is to use the tools we have available to make it as hard as possible for this virus to spread," Malcolm said. "In addition to vaccination and boosters, we can slow the spread of this variant and all COVID-19 variants by using the tried-and-true prevention methods of wearing masks, staying home when sick, and getting tested when appropriate."

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The department added that Minnesota epidemiologists will continue to investigate in collaboration with New York City and the U.S. Centers for Disease Control and Prevention (CDC).

New York City Mayor Bill de Blasio on Thursday urged anyone who had attended the Anime NYC 2021 convention -- and especially anyone experiencing COVID-19 symptoms -- to "get tested immediately and take additional precautions, including social distancing."

"We are aware of a case of the Omicron variant identified in Minnesota that is associated with travel to a conference in New York City, and we should assume there is community spread of the variant in our city," de Blasio said in a statement. "We are working closely with the State and the CDC, as well as the Javits Center’s event organizers, and our Test and Trace Corps will be contacting conference attendees. This conference required masks and complied with our Key2NYC requirement to mandate vaccination."

Speaking to reporters, New York Gov. Kathy Hochul said there are no confirmed cases of omicron in the Empire State but warned residents to be prepared and not panic. 

"We are ready unlike in March 2020," said Hochul.

New York Lt. Gov. Kathy Hochul gives a news conference at the state Capitol on Wednesday, Aug. 11, 2021, in Albany, New York.

New York Lt. Gov. Kathy Hochul gives a news conference at the state Capitol on Wednesday, Aug. 11, 2021, in Albany, New York. (Hans Pennink,/AP Photo)

White House press secretary Jen Psaki told reporters that she was not aware of any other omicron variant-linked cases in the U.S.

"I would note … even the restrictions we put in place [were] not going to prevent this variant from coming here. It would just slow. That was the objective," she said. "So, we do anticipate there will be more cases, and we know that will be the case, and that's why we're focused on doing everything we can to fight the virus and the variant."

Psaki pointed out that scientists are still determining whether omicron is less or more deadly than other variants.

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In a statement shortly after her remarks, the CDC said it was working with the Minnesota Department of Health and the New York City Department of Health and Mental Hygiene to investigate the case.

"CDC has been actively monitoring and preparing for this variant. We have been working closely with Minnesota’s Department of Health and will continue to work diligently with other U.S. and global public health and industry partners as we learn more," CDC Director Rochelle Walensky said. "CDC has expanded its capacity for genomic sequencing over the past nine months and we have more tools to fight the variant than we had at this time last year."

The agency recommends that people follow COVID-19 prevention strategies.