The first case of a new and potentially more infectious strain of Covid-19 has been confirmed in the United States, Colorado health officials said Tuesday.

Colorado health officials confirmed the case and notified the Centers for Disease Control and Prevention. The infected individual is in isolation in Elbert County, about an hour and a half south of Denver. Officials said the man, who is in his 20s, does not have a travel history.

“There is a lot we don’t know about this new Covid-19 variant, but scientists in the United Kingdom are warning the world that it is significantly more contagious. The health and safety of Coloradans is our top priority and we will closely monitor this case, as well as all COVID-19 indicators, very closely”, - Colorado Governor Jared Polis said.

“We are working to prevent spread and contain the virus at all levels”, - Polis said, adding that public health officials were working to identify other potential cases through contact tracing interviews.

Preliminary analysis of the mutated strain, first identified in the U.K., suggests it may be the culprit behind Britain’s recent spike in cases. The new strain, referred to as SARS-CoV-2 VUI 202012/01 in the science community, could be as much as 70% more transmissible, British Prime Minister Boris Johnson said.

The CDC said in December that the new strain could already be circulating in the U.S. without notice. The CDC cited ongoing travel between the U.K. and the U.S. as an explanation for the potential arrival of the new variant.