EG.5.1? BA.2.86? Keeping Up With the New COVID-19 Subvariants

For weeks, the COVID-19 subvariant EG.5.1, unofficially nicknamed “Eris,” dominated the news. Shortly after, headlines about BA.2.86, also known as “Pirola,” quickly arose. As word of new subvariants seems to spread infectiously through the media almost as rapidly as viral transmission itself, keeping up with all the new letters and Greek names can be overwhelming.

Yale School of Public Health’s Grubaugh Lab describes Anne Hahn, PhD, a postdoctoral associate who leads the Yale SARS-CoV-2 Genomic Surveillance Initiative, as the “variant hunter.” (She and her colleagues prefer not to use the new subvariants’ unofficial names to avoid further confusion if the World Health Organization (WHO) decides to assign them an official Greek letter.) Using nasal swabs obtained from routine patient testing at Yale New Haven Hospital, the team at the Yale School of Public Health sequences the genomes of the latest viruses and scours the letters of RNA code for any mutations of concern. While both EG.5.1 and BA.2.86 contain mutations that may help them evade the immune system, she isn’t sounding any alarm bells yet.

“Previously, before much of the population had some form of immunity, a new variant meant a new wave of infections. It’s a very different situation now,” says Hahn. “We see a lot of variants that could possibly be concerning, but never really take off. So it’s a bit hard to say at this point how dangerous these new variants are.”

EG.5.1 is an offshoot of an earlier Omicron subvariant known as XBB.1.9, a close relative to the XBB.1.5 that has been dominant since December 2022. It caught the attention of researchers because of two significant mutations in its spike protein that allow the virus to escape the body’s defenses. And in the weeks following its detection, the subvariant spread more rapidly than other lineages. “That’s why scientists thought it might have a big advantage compared to other variants and could be problematic,” Hahn explains. But now, more than a month in, experts feel more assured that EG.5.1 is not a substantial threat.

On the other hand, BA.2.86, says Hahn, is the much more interesting subvariant. It evolved from an Omicron BA.2 sublineage that was dominant way back in early 2022. “It’s derived from a subvariant that is very old and isn’t circulating anywhere in the world anymore,” says Hahn. “So it was surprising to see where it came from.”

This latest subvariant was first detected by surveillance labs in Israel and Denmark. Soon after, it popped up in labs in England, South Africa, and the United States. It has since been detected in wastewater in New York City. “It’s not in our samples [in New Haven] yet, but it’s at our doorstep,” says Hahn.

Researchers expect the new COVID-19 boosters that are arriving this fall to be effective against EG.5.1. But with almost 30 mutations on BA.2.86’s spike protein, there is concern that this subvariant may be able to more easily evade the immunity acquired from the jab. “If this BA.2.86 really takes off and is competitive with these other lineages, this could mean that many people might be reinfected because it just looks very different from what their immune systems recognize from previous vaccines or infections,” says Hahn.

It is still too early to know if BA.2.86 will cause a significant wave of infections. But as winter approaches, Hahn says that getting a booster is a good idea to improve your protection. “Even if this other variant takes over, it’s always good to boost your immunity as we enter a season where you will almost certainly encounter the (SARS-CoV-2) virus a couple of times,” she says. “It’s better to be prepared.” Also, Hahn says, regardless of which variant might emerge now or in the future, methods to reduce your risk of infection, as always, include staying home and testing when feeling sick and having a facemask handy for when you spend significant time indoors with many people.