A new Omicron subvariant, which is believed to be one of the drivers of a COVID-19 resurgence in Europe, now accounts for more than half the new cases in New England, according to estimates from the CDC.

The subvariant, known as BA.2, accounted for 55.4 percent of cases in New England as of Saturday, continuing to elbow out other varieties of Omicron.

Nationally, BA.2 has grown to account for 34.9 percent of cases, up from 1 percent as recently as early February, according to the CDC estimates.

The increases come as the region — and the nation — have seen steep declines from the Omicron surge early this year to much lower cases, hospitalizations, and deaths.

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But is this the calm before the storm? Experts and officials are eyeing increases in cases and hospitalizations in Europe warily, wondering if what is happening in Europe could happen here.

Three factors are seen as possible contributors to the rise of COVID-19 in Europe: the more contagious BA.2 taking over from other subvariants of the virus; the reopening of society; and people’s waning immunity from vaccination or prior infection. All three ingredients are present here in the United States, experts have said.

Some are acknowledging that there will be an impact from BA.2 but saying it won’t be large. Dr. Anthony Fauci, the nation’s top infectious disease expert and an adviser to President Biden is one of them. “The bottom line is we likely will see an uptick in cases, as we’ve seen in the European countries, particularly the U.K.,” Fauci said Sunday on ABC-TV’s “This Week.” “Hopefully we won’t see a surge. I don’t think we will.”

Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, said, “It’s likely that BA.2 will become the dominant virus in the United States,” causing an increase in cases. But he said, “We’re probably not going to see a full-blown surge due to BA.2.”

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Experts say that people should prepare for BA.2′s arrival by making sure they’re vaccinated and boosted.

“I still think the best thing you can probably do for yourself, if you haven’t already had a booster, is you should go ahead and get one now,” said Larissa Thackray, a virologist at Washington University in St. Louis.

A Massachusetts Department of Public Health spokeswoman said, “DPH reminds everyone that the best protection against COVID-19 and its variants is to get vaccinated and receive a booster when eligible. DPH also advises that people should stay isolated if they develop symptoms, arrange to get tested for COVID-19, and follow all isolation, quarantine and masking guidance as advised by DPH.”

She also said residents should remember that “free treatment options are widely available to prevent severe illness and hospitalization from COVID-19, including monoclonal antibody infusions and oral therapeutics.”

The treatment is available for people who are at increased risk of severe illness, test positive for COVID-19, and have symptoms, she said.


Martin Finucane can be reached at martin.finucane@globe.com. Daigo Fujiwara can be reached at daigo.fujiwara@globe.com. Follow him on Twitter @DaigoFuji.