CDC Estimates Show BA.2.86 Variant Accounts for 8.8% of COVID-19 Cases

According to the Centers for Disease Control and Prevention (CDC), the BA.2.86 variant of COVID-19 now represents nearly 1 in 10 new cases in the United States. This estimate is almost triple the agency's previous estimate just two weeks ago. Among the regions with sufficient data, the BA.2.86 variant is most prevalent in the Northeast, where it accounts for 13.1% of cases in the New York and New Jersey area.

The recent figures mark the first time the BA.2.86 variant's prevalence has risen enough to be classified as a standalone variant in the CDC's estimates. Scientists initially alerted the public to the discovery of this highly mutated strain during the summer. Previously, the BA.2.86 variant was grouped with other BA.2 strains due to its low occurrence.

Until now, the majority of new COVID-19 cases were attributed to the XBB variant and its closely related descendants, such as the HV.1 and EG.5 variants, which are currently dominant nationwide.

The CDC's estimates for the prevalence of the BA.2.86 variant carry a significant margin of error. It is estimated that this variant could account for as little as 4.8% or as much as 15.2% of circulating SARS-CoV-2. However, the latest estimate of 8.8% as of November 25 is nearly triple the estimate from November 11, which was 3.0%. The CDC usually publishes its variant estimates every other Friday but delayed last week's release until after the Thanksgiving holiday weekend.

The World Health Organization (WHO) has also elevated the classification of the BA.2.86 variant and its descendants to a "variant of interest" due to the increase in cases associated with this strain. Early data suggests that the BA.2.86 variant does not cause more severe or different symptoms compared to previous strains, according to the WHO's risk evaluation on November 21. However, there has been a significant rise in reported cases of BA.2.86.

The CDC concurs with the WHO's assessment that the BA.2.86 variant likely poses a "low" public health risk at this time. The CDC states that the BA.2.86 variant does not appear to be driving increases in infections or hospitalizations in the United States.

These developments come as the CDC observes a renewed increase in indicators tracking the spread of COVID-19 across the country heading into the winter season. After weeks of slowing or flat trends, the CDC has reported an increase in emergency department visits related to COVID-19 nationwide, with virtually all regions of the country experiencing at least slight increases. The Midwestern region, covering states such as Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin, is seeing some of the highest increases, approaching levels not seen since early January.

The BA.2.86 variant's broad array of mutations did not initially allow it to surpass the XBB variant and its descendants since August. However, in recent weeks, scientists have observed a significant rise in a BA.2.86 descendant called JN.1, which has become the fastest-growing subvariant globally. Many cases of JN.1 have been reported in Europe, where BA.2.86 and its descendants are also increasing.

Authorities in France have attributed a substantial portion of the country's increase in BA.2.86 infections to the JN.1 variant, accounting for 10% of sequences in the country. Preliminary investigations have not revealed any concerning signals compared to other BA.2.86 infections, but further analysis is underway.

Recent data from the GISAID virus database suggests that up to a third of COVID-19 variants reported in U.S. labs are JN.1.

The CDC anticipates that JN.1, the most common version of the BA.2.86 variant in the U.S., and its subvariants will continue to increase in proportion among SARS-CoV-2 genomic sequences. The CDC has previously stated that current COVID-19 tests and treatments are expected to remain effective against JN.1, which is closely related to BA.2.86, except for a single change in its spike protein that may enable faster transmission. The agency also believes that this season's vaccines should provide similar protection against JN.1 as they do against the BA.2.86 parent variant.