DENVER, United States (AP) — A new variant of the coronavirus that may be more contagious has been found in a Colorado man who had not been travelling, triggering a host of questions about how the first US case of the new version showed up in the Rocky Mountain state.

The new variant was first identified in England, and infections are soaring now in Britain, where the number of hospitalised COVID-19 patients has surpassed the first peak of the outbreak in the spring. The new variant has also been found in several other countries.

Colorado officials were expected to provide more details at a news conference Wednesday about how the man in his 20s from a mostly rural area of rolling plains at the edge of the Denver metro area came down with the variant. Governor Jared Polis announced the case Tuesday, adding urgency to efforts to vaccinate Americans.

For the moment, the variant is likely still rare in the US, but the lack of travel history in the first case means it is spreading, probably seeded by travellers from Britain in November or December, said scientist Trevor Bedford, who studies the spread of COVID-19 at Fred Hutchinson Cancer Research Center in Seattle.

“Now I’m worried there will be another spring wave due to the variant,” Bedford said. “It’s a race with the vaccine, but now the virus has just gotten a little bit faster.”

The man is in isolation southeast of Denver in Elbert County, state health officials said.

Colorado Politics reported there is a second suspected case of the variant in the state according to Dwayne Smith, director of public health for Elbert County. Both of the people were working in the Elbert County community of Simla. Neither is a resident of that county — expanding the possibility that the variant has spread in the state.

Public health officials are investigating other potential cases of the variant, which was confirmed by the Colorado State Laboratory, and performing contact tracing to determine its spread.

Scientists in the United Kingdom believe the variant is more contagious than previously identified ones — though they have found no evidence that it is more lethal or causes more severe illness. Experts also believe the vaccines being given now will be effective against the variant.