Health officials say a Colorado National Guard member has the first reported U.S. case of COVID-19 variant and a second case is suspected in another Guard member.

Dr. Rachel Herlihy, the state's epidemiologist, said Wednesday that the two were deployed on Dec. 23 to a nursing home with an outbreak of the virus in a small town outside Denver.

She appeared in a virtual briefing with Colorado Gov. Jared Polis, who says the man in his 20s with the confirmed case was recovering in isolation and had mild symptoms.

The new, mutated version was first identified in Britain, where infections are soaring and the number of hospitalized COVID-19 patients has surpassed the first peak seen last spring. The variant has also been found in several other countries.

"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," Colorado Gov. Jared Polis said. "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.”

The discovery of the mutated version overseas led the U.S. Centers for Disease Control and Prevention to issue rules on Christmas Day requiring travelers arriving from Britain to show proof of a negative COVID-19 test.