What to Know About New Covid Variants ‘Eris’ and BA.2.86

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EG.5 is spreading quickly, but experts say it’s no more dangerous than previous versions. Another new variant, called BA.2.86, is being closely watched because of its mutations.

By Dana G. Smith

Concern is rising about the Covid-19 variant EG.5. In August, it became the dominant variant in the United States, and the World Health Organization classified EG.5 as a “variant of interest,” meaning it has genetic changes that give it an advantage and its prevalence is growing. So how worried should people be about it?

While severe illness in older adults and people with underlying conditions is always a concern, as is long Covid in anyone who gets infected, experts say EG.5 does not pose a substantial threat — or at least no more of one than any of the other major variants currently circulating.

“It’s a concern that it’s increasing, but it doesn’t look like something that’s vastly different from what’s already been circulating in the U.S. for the past three to four months,” said Andrew Pekosz, a professor of molecular microbiology and immunology at Johns Hopkins University Bloomberg School of Public Health. “So I think that’s what tempers my concern about this variant, at this point in time.”

Even the W.H.O. stated in its announcement that, based on the available evidence, “the public health risk posed by EG.5 is evaluated as low at the global level.”

The variant was identified in China in February 2023 and was first detected in the United States in April. It is a descendant of the Omicron variant XBB.1.9.2 and has one notable mutation that helps it to evade antibodies developed by the immune system in response to earlier variants and vaccines. That advantage may be why EG.5 has become the dominant strain worldwide, and it could be one reason Covid cases have been rising again.

That mutation “may mean that more people are susceptible because the virus can escape a little bit more of that immunity,” Dr. Pekosz said.

But EG.5, which has also been called Eris, does not appear to have any new capacities when it comes to its contagiousness, its symptoms or its likelihood of causing severe illness. Diagnostic tests and treatments such as Paxlovid continue to be effective against it, Dr. Pekosz said.

Dr. Eric Topol, executive vice president of Scripps Research in La Jolla, Calif., said he isn’t overly worried about the variant; however, he would feel better if the new vaccine formulation, which is expected to be rolled out in the fall, was already available. The updated booster was developed based on another variant that is genetically similar to EG.5. It is expected to provide better protection against EG.5 than last year’s shot, which targeted the original coronavirus strain and a much earlier Omicron variant that is only distantly related.

“My main concern is for the people at high risk,” Dr. Topol said. “The vaccines that they’ve had are too far removed from where the virus is right now and where it’s going.”

Experts are more apprehensive about other emerging variants that carry the same immune evading mutation as EG.5, plus another mutation that makes the virus more transmissible. Scientists have nicknamed the combination of these mutations “FLip,” because they both flip the positions of two amino acids, labeled F and L. While these FLip variants make up only a small proportion of Covid cases currently, they could trigger a greater increase in infections in the coming months.

“I’m generally very concerned about the overall rate of evolution for SARS-CoV-2,” said Trevor Bedford, a professor in the vaccine and infectious disease division at Fred Hutchinson Cancer Center. “No single variant has been that impactful, but the overall accumulation of these mutations is having significant impact.”

Another new variant that scientists are watching closely is BA.2.86. Descended from a different Omicron variant, BA.2.86 has been definitively tied to seven cases of Covid worldwide, but experts suspect it is more widespread.

Scientists are particularly concerned about this variant because of the number of mutations it carries. Many of the mutations are in the spike protein, which is what the virus uses to infect human cells and what our immune systems use to identify it. According to Jesse Bloom, also a professor at the Fred Hutchinson Cancer Center who specializes in virus evolution, the mutations in BA.2.86 represent “an evolutionary jump similar in size” to the changes in the first Omicron variant compared to the original coronavirus strain.

However, many experts have urged people not to panic. It’s still way too early to know if vaccines and other forms of pre-existing immunity will be ineffective against BA.2.86, or if the variant will be more contagious or lead to more severe disease.

In an email to The New York Times, Dr. Bloom wrote: “One possible scenario is BA.2.86 is less transmissible than current variants, and so never spreads widely. This is the fate of most new SARS-CoV-2 variants. However, there is also a chance that the variant will spread widely — and we will just have to wait for more data to know.”

Dana G. Smith is a reporter for the Well section, where she has written about everything from psychedelic therapy to exercise trends to Covid-19. More about Dana G. Smith