Just one week after BA.5 had outcompeted all other Covid strains become dominant in the U.S., a new highly-mutated Omicron subvariant has arrived which may begin the cycle all over again.
BA.2.75 has a large number of mutations when compared to its sister Omicron lineages. Some of those adaptations could allow the virus to bind onto cells more efficiently, said Matthew Binnicker, director of clinical virology at the Mayo Clinic in Rochester, Minnesota. BA.2.75 was first sequenced in May in India, where it has spread rapidly.
A very early analysis of data from India by Raj Rajnarayanan — who is Assistant Dean of Research, NYITCOM at Arkansas State University — indicates that BA.2.75 may have a growth advantage over BA.5. It is unclear, as yet, whether BA.2.75 makes people sicker than previous variants.
BA.2.75 (#Centaurus) still didn’t remove its foot from the gas pedal in India!
Growth advantage of BA.2.75 vs BA.5* and BA.2.38* picked up some steam to 324% and 423% (over last 3 months)
Only one thing is sure… It Ain’t Over Folks! https://t.co/ywTyv00PAV pic.twitter.com/94Kj50OuNu
— Raj Rajnarayanan (@RajlabN) July 13, 2022
Since it was first identified, the subvariant has been spotted in “about 14 countries,” according to WHO Covid-19 Technical Lead, Maria Van Kerkhove. Those include Australia, Canada, Japan, Germany, New Zealand, the United Kingdom and the U.S.
States with sequenced BA.2.75 infections are California — with two cases — and one each in Illinois, New York, North Carolina, Texas, Wisconsin and Washington. The California cases were found in Bay Area wastewater samples from mid-June, reported the San Francisco Chronicle.
“It’s still really early on for us to draw too many conclusions,” said Binnicker. “But it does look like, especially in India, the rates of transmission are showing kind of that exponential increase.”
Tom Peacock, Virologist at Imperial College London cited “the divergent mutation profile, the wide geographical spread, and the rapidness that new sequences have emerged” as his chief concerns about BA.2.75. It also may have an advantage over BA.5 via increased immune escape.
“Over the last several months, we’ve seen each successive (Omicron) variant have a bit of a transmission advantage over the prior one,” said Dr. Anthony Fauci in the White House Covid-19 Response Team briefing on Tuesday. He presented a chart illustrating the stairstep nature of new variants’ rising growth capacity.
WHO’s Van Kerkhove cautioned that, for BA.2.75, “there are very few sequences that are available,” and so our understanding of the Omicron offshoot is limited.
Indeed, Covid surveillance funding has been cut worldwide and in the U.S. at federal, state and local levels, making it more difficult to understand what’s happening — or what will happen.
But if BA.2.75 does outcompete BA.5, it may follow a similar pattern to its predecessor variants, remaining at low levels for the next month or so and then roughly doubling in its share of new cases every week for the following month before becoming the dominant variant stateside about 12 weeks after discovery. That would put the nation in the grip of a new Covid surge as kids go back to school in September, roughly the same period when the Delta wave hit last year.