Analysis: What the BA.5 Subvariant Could Mean for the United States

What the BA.5 Subvariant Could Mean for the United States The most transmissible variant yet of the coronavirus is threatening a fresh wave of infections in the United States, even among those who have recovered from the virus fairly recently. The New York Times

The most transmissible variant yet of the coronavirus is threatening a fresh wave of infections in the United States, even among those who have recovered from the virus fairly recently.

The subvariant of Omicron known as BA.5 is now dominant, according to federal estimates released Tuesday, and together with BA.4, another subvariant, it is fueling an outbreak of cases and hospitalizations.

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Though the popularity of home testing means reported cases are a significant undercount of the true infection rate, the share of tests that come back positive is shooting upward and is now higher than during most other waves of the pandemic. According to the C.D.C., the risk from Covid-19 is increasing in much of the country.

“I think there’s an underappreciation of what it’s going to do to the country, and it already is exerting its effect,” said Eric Topol, a professor of molecular medicine at Scripps Research, who has written about the subvariant.

BA.5 and BA.4, both subvariants of the Omicron variant that swept the world during the winter, are the most capable versions of the virus yet at evading immunity from previous infections and vaccines. Both variants have mutations in their spike proteins that are different enough from earlier versions of the virus that they are able to dodge some antibodies.

Waves of infection — and the subsequent immunity that comes with them — vary across countries and make for imperfect comparisons. Vaccination rates also vary. But in places where BA.4 and BA.5 have been dominant for weeks or months, the subvariants have caused increases in cases and hospitalizations, despite some population immunity from previous waves.

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The C.D.C. says there is so far no evidence that BA.4 or BA.5 is inherently more severe than other Omicron subvariants, but when more people become infected, the number of people hospitalized because of the virus may also rise.

Prior infection with another form of the Omicron variant does confer some degree of immunity, Dr. Topol said, and that may explain why cases have not yet taken off sharply in the United States. “But it’s not anything like what we would hope,” he said. Omicron subvariants appear to represent a departure from earlier waves of the virus, when prior infection was more likely to protect against reinfection.

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