What to know about the newly dominant ‘Eris’ COVID variant

As summer winds down, there’s a new COVID variant on the rise. EG.5.1, nicknamed the “Eris” variant, has become the dominant strain in the US, making up 17.3 percent of cases in the US. 

The variant is a descendant of the Omicron, which itself had become the dominant COVID subtype by fall 2022. There’s not a lot of data right now on how severe or infectious this subvariant is compared to its parent strain or the other ones we’ve faced in the past. But based on its increasing caseloads, experts like Scott Roberts, an infectious disease specialist at Yale University, predict this one will stick around through the winter. “The question is how long will it stay, and will [Eris] continue to evolve in a few months.”

Fortunately, this isn’t 2020. We’re more prepared to treat COVID. Updated vaccine boosters are on the way this fall that will provide immune defenses against these types of strains. “We are optimistic that the new, updated boosters will offer ample protection against this current variant,” as Roberts says.

Where did Eris come from?

The EG.5.1 variant has been unofficially called Eris on social media after the Greek goddess of chaos, strife, and discord. Genetic sequencing suggests it is a descendant of an Omicron subvariant called XBB1.5, which was responsible for an outbreak of COVID infections earlier this year. “It’s part of this ongoing evolutionary tree from Omicron,” Roberts explains. Eris differs somewhat from others in the XBB lineage because there are new mutations on its spike protein, the part of the virus that lets it latch to and infect cells. 

Where is Eris spreading?

The World Health Organization has labeled Eris as a “variant of interest” as it spreads worldwide. Recently, it has caused COVID cases to spike in the UK. In the US, the latest CDC numbers show Eris is concentrated on both coasts. States like New York have been the hardest, with a 55 percent surge in COVID infections caused by the Eris variant above the previous week. Overall, though, the national test positivity rate is down to 9 percent, when it was nearly 14 percent this time last year, according to the CDC. 

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Linda Yancey, an infectious disease specialist at Memorial Hermann Health System in Houston, says health agencies likely noticed the outbreak in these two countries thanks to aggressive surveillance. “If we could expand out to the rest of the world, the picture would almost certainly look the same,” she says. There have been reports of Eris traveling through Asia, too, and possibly through Australia. 

Is Eris more contagious or dangerous?

The new variant still acts very similar to all the other Omicron strains, says Yancey. Evidence so far does not seem to suggest that it causes more severe illness, and the number of COVID deaths has not increased. The symptoms reported in Eris infections are familiar signs of COVID, including fever, cough, fatigue, and headaches.

In general, Omicron strains cause less severe disease because the virus doesn’t reach most people’s lungs, Yancey says. “So: Yay, they tend to cause less serious illness,” she says. “But, boo, they also tend to cause asymptomatic disease, so people don’t know they are infected and don’t isolate or wear masks.” No official studies have yet calculated Eris’s rate of transmission, and Yancey says that as a new strain it would make sense that it would at least be more contagious. “New strains have to out-compete old strains so the new ones are generally a little bit more easy to transmit.”

Do the vaccines protect against Eris?

There are no vaccines that specifically target EG.5, and scientists are still unsure whether these mutations help Eris bypass vaccine-induced immunity. However, since there are spike protein mutations and an increase in COVID hospitalizations, Roberts says the new variant is likely capable of thwarting some immune defenses. Still, he says, “we predict that vaccine immunity will still hold up quite well against this new Eris variant.” 

From his experience, the ones who remain most at risk appear to be the unvaccinated. “In our hospital, we have seen almost a tripling or quadrupling over the past several weeks,” Roberts adds, though cases remain “well below what we saw last summer and winter.” People who are not vaccinated or have not received all of the shots make up the majority of those hospitalizations. 

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For people who are unvaccinated, Roberts advises not to wait and to get last year’s bivalent booster. He says it should still provide some protection against this current variant, because it is a descendent of Omicron, which that vaccine has shown to protect against. 

Those who are up to date on their vaccinations do not need to re-up again and should instead wait for October’s booster. The new booster won’t include the specific EG.5 subvariant, but it will target the XBB strains. Both Roberts and Yancy recommend getting the booster when it rolls out this fall.

How concerned should we be?

Both infectious disease experts agree people need to be aware of—but not worried about—Eris. Expect to see a wave of cases as the US enters the winter months, but it should not be as big as those in past years. “We have a lot of herd immunity now compared to where we were a year ago,” says Roberts. “Every year as we go on, we’ll see successive decreases in the severity of waves.”

Beyond getting an updated booster, Roberts says to assess your personal risk tolerance levels. While we shouldn’t foresee any mask mandates, if you fall under the high-risk category, it’s a good idea to mask up when in crowds or indoor spaces with poor ventilation. You’ll want to keep some rapid COVID tests at home in case you need to test. Continue washing your hands and staying home when you’re sick to avoid getting and spreading Eris to others.