The case appears to be the first known case of that variant in the U.S.
Fauci: US taking hard look at variant of coronavirus that set off alarms in UK
Colorado officials said the man, who's had no travel history, is in isolation in Elbert County.
"Public health officials are doing a thorough investigation," a press release from the governor's office said. "The individual has no close contacts identified so far, but public health officials are working to identify other potential cases and contacts through thorough contact tracing interviews."
The variants are all the same virus, no matter their small genetic differences.
SARS-COV-2 is a respiratory virus, meaning it is transmitted through droplets, so masks and social distancing still work to slow transmission, no matter the variant.
Earlier this week Dr. Anthony Fauci said the variant strain is something "to follow very carefully."
Millions told to cancel Christmas plans in UK as new COVID-19 strain drives rapid spread
European Union nations have banned flights from the U.K. and Germany was considering limiting such flights to make sure that a new strain sweeping across southern England does not establish a strong foothold on the continent.
Japan sharply tightens ban on foreign visitors as a precaution against new and potentially more contagious coronavirus variant
British Prime Minister Boris Johnson has said the new variant of the virus is 70% more transmissible than existing strains and appears to be driving the rapid spread of new infections in London and southern England.
"There's no evidence to suggest it is more lethal or causes more severe illness," he said, or that vaccines will be less effective against it.
ABC News and The Associated Press contributed to this report.