The highly-contagious BA.5 omicron subvariant now accounts for 60% of all COVID-19 cases in New England and 65% across the U.S., according to Tuesday's update from the U.S. Centers for Disease Control and Prevention.
The BA.5 variant is now responsible for 59.7% of the region's cases, followed by BA.2.12.1 at 22.3%, BA.4 at 16.8% and BA.2 at 1.2%.
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Until last month, BA.4 and BA.5 hadn't made major inroads in the U.S., but that has changed dramatically in recent weeks.
How many cases of BA.4 and BA.5 are in New England?
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The latest data shows the two new subvariants have begun to spread rapidly, tripling from 24% to 76% of all cases in New England in the last three weeks. Nationally, BA.4 and BA.5 cases make up over 81% of COVID-19 cases, up from 70% just a week ago.
Doctors have warned in recent weeks that BA.4 and BA.5 could result in another outbreak here in the near future. Cases are rising in places like the U.K. and China, prompting some to consider a new round of lockdowns or mask mandates.
Three top Boston doctors spoke about what the rise of these subvariants means for New England and whether residents should be concerned during a "COVID Q&A" discussion with NBC10 Boston this week.
When will COVID-19 cases decrease?
"What I'd say it looks like from my vantage point here -- in terms of cases and looking at wastewater and what's going on in the hospital -- is that we're just sort of stuck, that we've really plateaued," said Dr. Shira Doron of Tufts Medical Center. "And that, I think, is the BA.4 and 5 -- especially BA.5 -- not letting cases continue to decline after a wave."
"Really, the recurring theme here is new variants and subvariants will emerge that evade immunity from vaccines and prior infection," she added. "We can't ever know exactly what they're going to do to our case rates until we get there."
"I think clearly, BA.5 has become the predominant variant here in Massachusetts and across the U.S.," Dr. Daniel Kuritzkes of Brigham and Women's Hospital said. "We're way above where we were last year at this time in terms of case numbers, but fortunately we're also seeing much less in the way of critical illness, and that undoubtedly is a combination of the fact we have a highly vaccinated population here... and there's also a lot of acquired immunity from people who have had one or more episodes of COVID in the last 2-1/2 years."
Click here to learn more about the symptoms associated with the BA.4 and BA.5 omicron subvariants.
