Experts fear that the variant first found in the UK, known as B.1.1.7, will become the dominant strain in the US.
The US could see a “fourth surge” of coronavirus cases fuelled by the spread of variants, a top health official has warned.
Dr Rochelle Walensky, director of the US Centers for Disease Control and Prevention (CDC), said variants are a “real threat to our people and progress”, and that there was real concern of a possible fourth wave based on some concerning CDC data.
Declines in hospitalisations and deaths are also “potentially levelling off at still a very high number”, Dr Walensky said.
There are currently around 70,000 coronavirus cases a day and 2,000 daily deaths, Dr Walensky added.
Overall, the outbreak has killed more than half a million Americans.