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CDC data show sharp increase in COVID cases caused by BQ.1 and BQ.1.1 subvariants

A walk-up COVID test site at the Esperanza Heath Center in Chicago in September. One of the newest COVID subvariants can evade immune responses better than all earlier forms of Omicron.JAMIE KELTER DAVIS/NYT

The proportion of COVID-19 cases caused by the worrisome subvariants BQ.1 and BQ.1.1 has increased sharply, according to new estimates released Friday by the US Centers for Disease Control and Prevention.

The CDC estimates that immunity-evading BQ.1 and BQ.1.1 now account for 14 and 13.1 percent of the nation’s COVID-19 cases, respectively — more than a quarter. That’s up from 9.4 and 7.2 percent in estimates released last week.

As recently as Sept. 17, the two subvariants accounted for less than 1 percent of cases, according to CDC.

CDC and other scientists have been closely tracking a wide range of Omicron sublineages, including BQ.1 and BQ.1.1, which are offshoots of the BA.5 subvariant that’s been predominant for months. (BA.5 now accounts for less than 50 percent of cases.) The agency also has said it is keeping a close eye on the XBB subvariant. XBB is blamed for a spike in Singapore, but so far has been rare in the United States.

BQ.1.1. is a particular concern, experts have said. The subvariant is not only growing fast, it appears to be able to evade monoclonal antibody treatments for patients with weakened immune systems.

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Experts and officials are concerned new subvariants could cause a surge in cases in the cold months ahead. BQ.1 and BQ.1.1 are “present at significant levels,” and will likely “contribute to a further increase in cases” in Europe in the “coming weeks to months,” the European Centre for Disease Prevention and Control warned last week.

On the plus side: There is no sign so far that BQ.1, BQ.1.1, and XBB cause more severe disease than current versions of the virus, experts have said.

CDC data for the US so far aren’t showing any sign of a new surge. The pandemic is in a relative lull right now, with metrics at levels far lower than the original Omicron surge early this year.

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Still, COVID-19 continues to kill hundreds of people a day. An average of 390 people in the United States died daily of COVID-19 in the four-week period ending Wednesday, according to the CDC.

Federal officials have urged people to get their booster shots to ward off the virus.

“As a country, we have a choice to make,” President Biden said last week at the White House. “Can we repeat what happened in the past winters — more infections, more hospitalizations, more loved ones getting sick, even dying from the virus? Or can we have a much better winter if we use all — all — the tools we have available to us now?”

“Get vaccinated,” said Biden, who got his own booster last week. “Not enough people are getting it.”

Material from Globe wire services was used in this report.


Martin Finucane can be reached at martin.finucane@globe.com.