The BA.4 and BA.5 sub-variants of Omicron are estimated to make up nearly 5% and 8% of the coronavirus variants in the United States as of June 4, the US Centers for Disease Control and Prevention (CDC) said on Tuesday.
The two sublineages, which were added to the World Health Organization's monitoring list in March and designated as variants of concern by the European Centre for Disease Prevention and Control (ECDC), were present in all US regions.
Last month, South African scientists found that the sublineages of the Omicron coronavirus variant can dodge antibodies from earlier infection well enough to trigger a new wave.
BA.4 made up 5.4% of the variants in the country for the week ending June 4, according to CDC estimates, while BA.5 made up 7.6% of the variants during the same time.
The seven-day moving average of US COVID-19 cases stood at 98,010 as of June 4.