Los Angeles, Jul 13 (IANS): The newer and most contagious Omicron subvariants, known as BA.4 and BA.5, now make up more than 80 percent of Covid-19 infections in the US, according to data released by the US Centers for Disease Control and Prevention (CDC).

The BA.5 subvariant accounted for 65 per cent of new infections in the latest week ending July 9, while BA.4 accounted for 16.3 per cent of new infections, CDC data showed on Tuesday.

BA.5 has become the dominant variant in the US, Xinhua news agency reported.

Confirmed cases contracted by the two subvariants have kept increasing since mid-May, CDC data show.

The two subvariants are more contagious than earlier variants of Omicron, and also appear to evade protection from vaccines and previous infections more easily than most of their predecessors, according to health experts.

"Cases are already rising again in the US, and could rise substantially later this summer or in the fall, when there is a return to offices, schools, and other indoor facilities," Jeffrey Sachs, Professor and Director of the Center for Sustainable Development at Columbia University, told Xinhua in a recent interview.

Experts stressed that current public health tools, including masking indoors, avoiding crowds and getting booster shots, are still very effective against severe illness, hospitalisations and deaths caused by BA.4 and BA.5.