What to Know About ‘Eris,’ the New Dominant Covid Variant

Concern is rising about the Covid-19 variant EG.5. This week, 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 started to rise 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.”

Despite the growing number of mutations, it is highly unlikely these new variants will cause a surge akin to the one that occurred in the winter of 2022 with the first Omicron variant, Dr. Topol said. “It’s nothing like what we’ve been through with Omicron in terms of how much more transmissible” these variants are, he said. “But there will be more reinfections.”