New COVID variant BA.2.86 spotted in 10 states, though highly mutated strain remains rare

People across at least 10 states have now been infected by BA.2.86, a highly mutated variant of the virus that causes COVID-19 that authorities have been closely tracking.

According to data tallied from the global virus database GISAID, labs have reported finding BA.2.86 in samples from Colorado, Maryland, Michigan, New York, Ohio, Oregon, Pennsylvania, Texas, Virginia and Washington.

Estimates suggest BA.2.86 still remains a small fraction of new COVID-19 cases nationwide. 

Too few sequences of the virus have been reported to show up on the Centers for Disease Control and Prevention's biweekly variant estimates, which still show that a long list of closely related XBB variant descendants are driving virtually all infections around the country. 

"The diversity is less than what appears. Many of these lineages actually have identical spike sequences. We've observed this before, where we see convergent evolution and viruses evolving to have the same substitutions," said Natalie Thornburg, a laboratory branch chief in the CDC's Coronaviruses and Other Respiratory Viruses Division.

Thornburg, who was speaking at a meeting of the agency's vaccine advisers last week, said it was still too early to know "if BA.2.86 will be of any significant circulation."

Health authorities do believe BA.2.86 is continuing to spread widely around the world, after scientists first voiced concern in August over the strain's large number of mutations. 

"We are concluding this because some of the people infected with BA.2.86 do not have known links to other infected individuals and did not recently travel to an area with known cases of illness from BA.2.86," the CDC said Friday in a risk assessment.

Several countries have reported finding the variant in either wastewater samples or tests from people infected, including provinces in Canada. CDC's airport testing program has also picked up signs of the strain in arriving travelers from abroad.

While it remains too early to say how transmissible the variant could be compared to other strains on the rise, officials say BA.2.86 has so far proved it has the ability to drive outbreaks. 

Nearly two dozen nursing home residents were infected by the BA.2.86 variant in a cluster of cases late last month, officials in the United Kingdom reported.

"At this point, although we've got limited clinical data, on the cases who have been reported, there isn't evidence that it is causing more severe illness. But it's something we'll continue to track," Hanna Kirking, of the CDC's COVID-19 epidemiology task force, said Thursday at an event hosted by the Infectious Diseases Society of America.

Could BA.2.86 drive a new surge this winter?

The CDC has described early research findings as "reassuring" about the variant so far, suggesting it might not be as capable of evading the body's immune defenses as initially feared. 

Vaccine manufacturers have also said their data suggest the updated COVID-19 shots now being rolled out should also work against BA.2.86.

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Research on BA.2.86 so far has so far largely relied on pseudoviruses, which are other viruses mocked up in a lab to mimic BA.2.86's distinctive mutations. Better findings will need to use viruses grown from actual samples of infected patients, a process which is now underway.

"CDC has generated two authentic isolates of BA.2.86. One confirmed and one putative. We are in the process of distributing BA.2.86 viruses to multiple labs to do transmission studies, more neutralization studies, against lots of different kinds of sera," said Thornburg.

For now, officials have expressed "guarded hope" about signs the current late summer wave of COVID-19 driven by other variants has passed its peak. One leading indicator of the virus — emergency department visits — has been trending down in recent weeks.

Past years have seen renewed upticks of the virus return in the colder months, alongside influenza and RSV, or respiratory syncytial virus. The CDC says it's too early to figure out how the BA.2.8 variant will factor into its modeling for the coming respiratory virus season. 

Meanwhile, scientists have already tracked BA.2.86 beginning to evolve into at least two different branches. Cases from both sublineages have been spotted in the U.S. so far, among the handful of cases reported globally so far.

"That's likely the tip of the iceberg, given that we know we don't have complete sequencing coverage," Kirking said.

In:
• COVID-19 Vaccine
• COVID-19

Alexander Tin

CBS News reporter covering public health and the pandemic.