Yet another omicron subvariant is raising concern as BA.5 sweeps the US

Enlarge / MUMBAI, INDIA JUNE 7: A health worker collects swab samples of a citizen for Covid-19 test after cases are on the rise in the city, at TMC's C.R. Wadia Hospital testing centre, in Thane, on June 7, 2022 in Mumbai, India. (credit: Getty | Hindustan Times)

As the omicron coronavirus subvariant BA.5 blazes through the US—accounting for an estimated 54 percent of cases in the country—experts are eyeing another subvariant that threatens to follow hot on its heels.

The subvariant is referred to as BA.2.75 and was first detected in India in late May. Amid a backdrop of BA.2 and BA.5 circulating in India, the newcomer BA.2.75 began quickly gaining ground in June. This week it reached 23 percent of recent virus samples there. Meanwhile, spread beyond India's borders. It is now present in about 10 other countries, including the US, according to the World Health Organization.

Experts are concerned about the new subvariant, not just because of its rapid rise. It has several mutations in its spike protein—the critical protein that allows the virus to latch onto human cells and the protein that acts as a prime target for immune responses. In particular, BA.2.75 has key mutations that suggest it could be good at evading antibody responses in people who have been vaccinated and/or previously infected with earlier omicron subvariants.