The first reported US case of the highly-infectious Covid-19 variant that emerged in the UK has been confirmed in the state of Colorado.
The patient, a man in his 20s with no recent travel history, is currently in isolation.
State health officials said they were working to identify contacts and other potential cases of the new variant.
It came as US President-elect Joe Biden criticised the Trump administration’s distribution of vaccines.
He said the programme was falling behind schedule.
The US has recorded more than 19 million infections and more than 337,000 deaths from coronavirus, the highest figures in the world.
The new variant is considerably more transmissible than previous strains but not necessarily any more dangerous for those infected, experts say.
US health officials said last week that they believed it was already in circulation in the country.
In a statement on Tuesday, Colorado governor Jared Polis said the infected patient was in isolation in Elbert County near Denver.
Public health officials were carrying out “a thorough investigation”, he said, and no infections had been discovered among close contacts so far.
Cases of the new variant have been appearing in the world. The first two known infections on the North American continent came to light in Canada at the weekend.
Two coronavirus vaccines – one by Moderna and one by Pfizer – are currently being distributed and administered across the US.
The government had aimed to vaccinate 20 million Americans by the end of December. But so far, only 2.1 million have received shots, according to the US Centers for Disease Control and Prevention (CDC).
President-elect Biden said the vaccine drive was the “greatest operational challenge we’ve ever faced as a nation”.
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