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Meet the COVID-19 variants that experts say could fuel a surge this winter

A nurse prepared a COVID-19 booster shot at a vaccination site in Maywood, Ill., on Sept. 13.JAMIE KELTER DAVIS/NYT

By Martin Finucane Globe Staff, Updated October 26, 2022, 3:52 p.m.

Multiple variants are vying to succeed Omicron BA.5 as the leading cause of COVID-19 cases in the United States and the world, and experts are worried that one or more could drive a new surge in the months ahead.

“It is this constant evolutionary arms race we’re having with this virus,” Dr. Jonathan Abraham, an assistant professor of microbiology at Harvard Medical School, told The Washington Post last week.

Two particular strains have received an increased level of attention recently: BQ.1 and XBB.

BQ.1 and its sublineage BQ.1.1 are “present at significant levels in Europe,” and will likely “contribute to a further increase in cases” there in the “coming weeks to months,” the European Centre for Disease Prevention and Control said last week.

The US Centers for Disease Control and Prevention estimates that BQ.1 and BQ.1.1 now account for 9.4 and 7.2 percent of US cases, respectively, up from less than 1 percent as Sept. 17.

The Washington Post warned in an editorial this week that another COVID-19 “wave is on the horizon because of a new immunity-evading subvariant, BQ.1, and its offshoots.”

XBB has driven a surge in Singapore. But it has remained mostly on the sidelines in the United States, so far. It has not appeared yet in CDC estimates of variant prevalence.

Samuel Scarpino, vice president of pathogen surveillance at the Rockefeller Foundation, said he was worried about BQ.1.1 and XBB.

He said he expected BQ.1.1 to “almost certainly” outcompete XBB because the two have similar growth advantages and BQ.1.1 has gotten a head start. The foundation estimates that BQ.1.1 is already causing 20 to 25 percent of cases in the United States, while XBB is causing only 3 percent.

How bad could it get?

“The data coming out of lab studies pretty clearly shows BQ.1.1 and XBB are highly immune-evasive,” Scarpino said. “We also expect there will be a seasonal bump in COVID cases, and we know that the uptake rate of bivalent boosters has not been amazing. You put all those together, and it certainly looks like a surge is coming,” he said.

But there is “a huge amount of immunity” in the population from previous infections and vaccinations that makes predictions challenging, he noted.

He advised people to get their COVID-19 booster shots and, while they’re at it, get their flu shots as well. “Now is the time. You’ve got to go out and do it,” he said.

One piece of good news about the new variants is there is no sign so far that they are more severe than current versions of COVID-19, Dr. Maria Van Kerkhove, the World Health Organization’s technical lead for COVID-19, said Tuesday in a video discussion.

“I think what’s important out there for the viewers is that they understand that Omicron variants of concern are circulating. The virus is thriving right now because we have very few provisions in place to prevent infection transmission. Distancing, masking, improving ventilation, staying home if you’re unwell, making sure we have good surveillance — that’s not as strong as it was previously, and the virus is taking advantage of that. So among the 300 sublineages of Omicron, there are several that are on our radar. These two are ones to watch,” she said.

Experts have said they are worried about a possible replay of last year when the Omicron variant came seemingly out of nowhere toward the end of the year, causing tens of millions of infections and leading to some of the highest death rates of the pandemic. This year, officials are privately worried about limited funds, worn-out front-line health workers, and the dwindling receptivity of many Americans to COVID-19 precautions, the Post reported Wednesday.

“This virus is not going anywhere,” Van Kerkhove cautioned. “It will be with us, and we are still learning from it. These variants are showing us — long COVID is showing us — that we still have a lot to learn, and we need to remain humble to that.”

Matthew Fox, a professor of epidemiology and global health at the Boston University School of Public Health, said in an e-mail that there’s “no need to panic [about various variants] but we should be prepared to act if needed, and everyone should get boosted.”

Material from Globe wire services was used in this report.

Martin Finucane can be reached at