A variety of variants could fuel a winter COVID surge

XBB, BQ.1.1, BA.2.75.2 — a variant swarm could fuel a winter surge Multiple versions of the omicron variant, including XBB and BQ.1.1, threaten to knock out treatments and challenge vaccines this winter. Carolyn Y. Johnson Washington Post

For two years, coronavirus variants emerged, one by one, sweeping the globe.

But this fall and winter are expected to be different: Instead of a single ominous variant lurking on the horizon, experts are nervously eyeing a swarm of viruses — and a new evolutionary phase in the pandemic.

This time, it’s unlikely we will be barraged with a new collection of Greek alphabet variants. Instead, one or more of the multiple versions of the omicron variant that keep popping up could drive the next wave. They are different flavors of omicron, but eerily alike — adorned with a similar combination of mutations. Each new subvariant seems to outdo the last in its ability to dodge immune defenses.

“It is this constant evolutionary arms race we’re having with this virus,” said Jonathan Abraham, an assistant professor of microbiology at Harvard Medical School.

The pace of evolution is so fast that many scientists depend on Twitter to keep up. A month ago, scientists were worried about BA.2.75, a variant that took off in South Asia and spawned a cloud of other concerning sublineages. In the United States, BA.4.6 and BF.7 have been slowly picking up steam. A few weeks ago, BQ.1.1 started to steal the spotlight — and still looks like a contender to take over this fall in Europe and North America. A lineage called XBB looms on the sidelines, and threatens to scramble the forecast.

To focus too much on any one possible variant is, many experts argue, missing the point. What matters is that all these new threats are accumulating mutations in similar spots in what’s called the receptor binding domain — a key spot in the spike protein where virus-blocking antibodies dock. If those antibodies can’t dock, they can’t block. Each new mutation gives the virus a leg up in avoiding this primary line of immune defense.

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