The BA.2 sub-lineage of the Omicron variant now makes up about 35 per cent of new Covid-19 infections in the US, according to the data updated Tuesday by the US Centers for Disease Control and Prevention (CDC).
This data is up from 22.3 per cent a week prior, and 15.8 per cent two weeks before, Xinhua news agency reported.
The BA.2 variant is steadily gaining its hold in the country, with infections doubling in less than two weeks, according to CDC data.
Although the original Omicron variant still makes up the majority of Covid-19 infections in the country, its prevalence has dropped to 57.3 per cent in the week ending March 19.
Anthony Fauci, the nation's top infectious disease expert, said he expects "an uptick in cases" due to BA.2, but not necessarily a massive surge like other variants have caused.
Fauci told ABC on Sunday the new strain is about 50 to 60 per cent more transmissible than the first Omicron strain, adding that it could take over as the dominant strain in the US.