Four states in the U.S. have identified new cases of the omicron variant of the coronavirus.
On Thursday, health officials from Minnesota, New York, and Colorado announced cases of the new, highly mutated variant, one day after the Centers for Disease Control and Prevention reported the first individual detected with omicron in California.
The three cases in California, Minnesota and Colorado have been mild and those individuals are recovering, health officials say.
New York Gov. Kathy Hochul announced Thursday evening that the state had confirmed five cases of the omicron variant.
"Let me be clear: This is not cause for alarm. We knew this variant was coming and we have the tools to stop the spread," Hochul said. "Get your vaccine. Get your booster. Wear your mask."
Hochul held a joint news conference with New York City Mayor Bill de Blasio, telling reporters that the early cases appear to be minor, non-life-threatening cases at this time.
A 67-year-old woman in Suffolk County who traveled to South Africa tested positive Nov. 30 following mild symptoms upon returning home. She had received at least one vaccination, but it was unclear whether the woman was fully vaccinated, Hochul said.
Two other cases were from individuals in Queens and one in Brooklyn, but their vaccination status was unknown.
The fifth case was identified in New York City from a traveler, but Hochul did not have further details.
Minnesota's Department of Health said an adult male, who lives in Hennepin County, was found to have the variant. He was vaccinated about six months ago and had gotten his booster shot in early November, officials with the department said during a briefing Thursday.
He had mild symptoms on Nov. 22, which have since resolved.
He told the Minnesota Department of Health that he had traveled to New York City to attend the Anime NYC 2021 convention at the Javits Center on Nov. 19-21.
Minnesota health officials are working with New York health officials to determine who the man may have had contact with. He hadn't traveled internationally, and officials with the Minnesota Health Department said it's most likely that transmission of the virus happened at the convention.
A statement from the Javits Center, which at one point was a New York City vaccination center, said visitors are required to show proof of vaccination and wear masks indoors.
Because the Minnesota man attended the convention, it's likely the variant is spreading in New York City, health commissioner, Dr. Dave Chokshi, said on Twitter Thursday, urging attendees of the convention to be tested immediately and take precautions such as wearing a mask and social distancing.
It's unclear whether the new cases in New York were related to the convention at the Javits Center, Hochul and de Blasio said, noting that contact tracing had only just begun.
One person close to the man, in Minnesota, has tested positive for coronavirus with a rapid test, officials said. The result is under investigation, and the person is isolating, they said.
Gov. Tim Walz said the "news is concerning, but it is not a surprise."
"We know that this virus is highly infectious and moves quickly throughout the world," he said.
A female resident of Colorado has also contracted the variant strain of the virus, the state's department of health confirmed Thursday. The woman, who lives in Arapahoe County, had recently traveled to South Africa and was fully vaccinated, but had not yet received a booster shot.
She is experiencing mild symptoms and isolating in her home, according to Colorado Department of Health and Environment.
On Wednesday, the CDC and the California Department of Public Health and the San Francisco Department of Public Health identified a traveler who returned from South Africa on Nov. 22 as the first confirmed case of the omicron variant in the U.S. — three days before scientists in that country announced they'd identified the new variant.
The person in California, an adult under age 50, developed symptoms a few days after arriving in the U.S. and got tested on Nov. 28, California Gov. Gavin Newsom said in a briefing Wednesday. The test came back positive for Covid-19 on Monday, Nov. 29.
"The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has been since testing positive," the CDC reported in a statement.
Close contacts of the California case have been undergoing Covid tests and so far, no one has tested positive. The individual from California was fully vaccinated with two doses of the Moderna vaccine, but had not been eligible to receive a booster shot.
The omicron variant has a high number of mutations that suggest it may spread just as or more easily than the delta variant, which accounts for 99.9 percent of Covid cases in the U.S.
Scientists have cautioned that it's still unclear whether omicron is more dangerous than other versions of the virus that has killed more than 5 million people worldwide. It is also unknown how well the vaccines and treatments would work against the variant.
The World Health Organization said Monday that the global risk of the new variant is "very high."
Meanwhile, public health experts continue to recommend tried-and-true ways of Covid protection: vaccination and a booster, wearing masks indoors and in crowded spaces, and continued physical distancing.
The variant has been detected in the United Kingdom, the Netherlands, Italy, Portugal, Germany, Belgium, Canada, Australia, Israel and Hong Kong, among other countries.
While world leaders and health experts are urging people to get vaccinated as soon as possible, some countries are struggling to inoculate their populations due to lack of access.
Follow NBC HEALTH on Twitter & Facebook.