Another omicron sub-variant sparks concern as BA.5 sweeps the US

Enlarge / MUMBAI, INDIA JUNE 7: A health worker takes swab samples from a citizen for Covid-19 testing after the rise in cases in the city, in testing center at C.R. Wadia Hospital of TMC, Thane on June 7, 2022 in Mumbai, India. Getty | Hindustan time

As the omicron coronavirus subvariant BA.5 spreads in the United States, accounting for about 54% of cases in the country, experts are eyeing another subvariant that threatens to follow closely behind .

The subvariant is called BA.2.75 and was first detected in India in late May. Against a backdrop of BA.2 and BA.5 circulating in India, newcomer BA.2.75 started to gain traction rapidly in June. This week, it reached 23% of recent virus samples. Meanwhile, BA.2.75 has spread beyond India's borders. It is now present in a dozen other countries, including the United States, according to the World Health Organization.

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

"This subvariant appears to have some mutations on the receptor binding domain of the spike protein, so obviously that's a key part of the virus that attaches to the human receptor, so we need to watch that," World Health Organization chief scientist Dr. Soumya Swaminathan said in an explanatory video this week.

Swaminathan notes that, for now, the number of samples and sequences is still low, and our understanding of this version of the virus is limited. "It's still too early to know if this subvariant has additional immune evasion properties or, in fact, to be more clinically severe. We don't know. So we have to wait and see," she said, adding that the WHO is closely monitoring the subvariant.

Status in the United States

So far, three cases of BA.2.75 have been detected in the United States, which have been identified in California and Washington State. Helix — a California-based viral surveillance company that works with the Centers for Disease Control and Prevention to track emerging coronavirus variants — confirmed the third U.S. case in Ars in an email Friday. Specimens for the three US cases were collected on June 14, 15, and 27.

Helix said it's still too early to predict how BA.2.75 will play out in the US, but the sub-variant is worth watching, echoing warnings from outside experts.

In the meantime, BA.5 is sweeping the United States. The prevalence of the previous reigning omicron subvariant, BA.2.12.1, has fallen to around 27%. BA.4 - a subvariant that shares the same spike mutations as BA.5 and has spread alongside BA.5 elsewhere - appears to have stagnated, accounting for only 16.5% of cases in the United States.

Amid the BA.5 increase, cases have maintained a high plateau, although many cases detected by rapid home tests are not being reported. According to New York Times tracking, the country is averaging around 108,000 new cases per day. Some experts are eagerly waiting to see if there will be a bump after the Independence Day celebrations. Just before the holidays, the reported test positivity rate reached 17.5%.

Otherwise, daily hospitalization...