The US national public health agency said on Tuesday (Apr 12) the BA.2 sub-variant of Omicron was estimated to account for 85.9 per cent of the coronavirus variants in the country.
A resurgence in COVID-19 cases in parts of Asia and Europe has raised concerns that another wave could follow in the United States, but the country's health experts believe it is unlikely.
The US Northeast, including New Jersey, New York and Massachusetts, is the hardest hit region across the country, with Omicron BA.2 now accounting for more than 90 per cent of the cases.
Philadelphia, a city in the northeastern state of Pennsylvania, will reimpose its indoor mask mandate from Apr 18, as a response to a fresh wave of cases. According to a Reuters tally, COVID-19 cases in Pennsylvania have risen nearly 70 per cent within a week as of Sunday, making it among the top 10 states where infections are spreading fastest.
The seven-day moving average of US COVID-19 cases stood at 28,339 as of Apr 9, up nearly 10 per cent from a week earlier.
BA.2 made up 75.4 per cent of the variants in the country for the week ending Apr 2, according to estimates from the US Centers for Disease Control and Prevention. That compared with a previous estimate of 72.2 per cent.