As China scales back restrictions amid surging COVID-19 cases, experts are worried about whether BF.7, the dominant strain there, could mean trouble for the U.S.
The BF.7 subvariant, which descended from the BA.5 strain, is extremely adept at evading immunity and is believed to be driving China's current surge. In the U.S., BF.7 currently accounts for just 3.9% of cases and about 3.2% in New England, data from the U.S. Centers of Disease Control and Prevention shows.
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Experts explained whether or not they're worried that the surge in China could unleash a new coronavirus mutant on the world during the latest episode of NBC10 Boston's weekly "COVID Q&A" series.
"What I'm worried about, honestly, is — with a massive explosion of cases in China — the potential for a new variant to evolve in that context that could be even more resistant to our current treatments and to our immunity. And that could spread globally," Boston Medical Center's Dr. David Hamer said. "But, you know, time will tell."
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Every new infection offers a chance for the coronavirus to mutate, and the virus is spreading rapidly in China. The country of 1.4 billion has largely abandoned its "zero COVID" policy. On Wednesday, the U.S. announced it would soon require travelers from China to provide a negative COVID test before flying in.
Though overall reported vaccination rates are high, booster levels are lower, especially among older people. Domestic vaccines have proven less effective against serious infection than western-made messenger RNA versions. Many were given more than a year ago, meaning immunity has waned.
The result? Fertile ground for the virus to change.
"I think it is certainly a possibility that a completely new variant could emerge from the millions of cases that are likely to be happening now in China," Brigham and Women's Hospital's Dr. Daniel Kuritzkes said.
About three years ago, the original version of the coronavirus spread from China to the rest of the world and was eventually replaced by the delta variant, then omicron and its descendants, which continue to plague the world today.
Partially immune populations like China's put particular pressure on the virus to change, experts say. One big unknown is whether a new variant will cause more severe disease.
"Whether that would have a serious impact in terms of hospitalizations and deaths is impossible to predict," Kuritzkes said, "because it would depend, first of all, on the nature of the variant and secondly, whether all of the other non-spike directed immunity that has developed in the population is going to be sufficient to control the severity of those infections as it did with omicron."
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In China, most people have never been exposed to the coronavirus. China's vaccines rely on an older technology producing fewer antibodies than messenger RNA vaccines. Given those realities, experts say it remains to be seen if the virus will follow the same pattern of evolution in China as it has in the rest of the world after vaccines came out.
"There are going to be a lot of infections in China, and it's likely to affect them more because they don't have natural immunity and they may be under-vaccinated, or particularly high risk people may be under-vaccinated, but there are plenty of infections and already were plenty of infections throughout the rest of the world," Tufts Medical Center's Dr. Shira Doron said. "It wasn't causing as much hospitalization and death because there was immunity, but there was plenty of circulating virus, so I'm not sure that we need China to help us get more new variants when we already had plenty of opportunity for new variants to develop throughout the entire rest of the world."
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The Associated Press contributed to this report.
