What we know about new coronavirus variant 'Eris,' from symptoms to how fast it's spreading

• A coronavirus variant nicknamed "Eris" is now thought to be the dominant strain in the US.
• The variant was discovered in February, and exploded during the summer months.

A new coronavirus variant is rearing its head across the United States. Dubbed "Eris," it's descended from XBB — the same Omicron subvariant that spun off the "kraken" variant this past winter.

"It started off very slowly and then it seems to be picking up steam in terms of outcompeting its predecessors," John Swartzberg, an infectious-disease expert who's a professor emeritus at the University of California at Berkeley's School of Public Health, told Insider.

Eris, formally known as EG.5, was named for the Greek goddess of strife in a tweet by the evolutionary biologist T. Ryan Gregory. "Eris" (also the name of a dwarf planet in our solar system) aligns with guidance from the World Health Organization to use "simple, easy-to-say labels" for coronavirus variants using letters from the Greek alphabet.

But though the CDC says Eris is spreading quickly, it doesn't appear to make people sicker than other variants, and symptoms of COVID-19 infection are similar to those caused by other strains.

Eris is now considered the dominant coronavirus strain in the US

Eris first emerged in February and is an offshoot of the Omicron subvariant XBB. But it really began to take off in July, when its estimated share of total cases doubled.

Eris accounted for fewer than 1% of COVID-19 cases in the US at the end of April, according to the Centers for Disease Control and Prevention. But it is now estimated to account for more than 20% of new US COVID-19 cases, the CDC says.

Scientists aren't yet sure why Eris is now so common, but its dramatic increase led the World Health Organization to upgrade Eris from a "variant under monitoring" to a "variant of interest" in early August. In other words, WHO believes Eris poses an increased risk to global public health.

"Based on its genetic features, immune escape characteristics, and growth rate estimates, EG.5 may spread globally and contribute to a surge in case incidence," an August 9 WHO report said.

"Everything we've seen to date with this variant suggests that it has properties that allow it to be a little more transmissible than its competitors," Swartzberg said. "We've not seen any evidence to date that it is more virulent. That is, it makes us sicker."

Swartzberg added, however, that our understanding of Eris is "still very early in the game — we haven't adequately been able to study enough people with EG.5 to know with certainty that it doesn't make us sicker, or conversely that it makes us less sick."

Symptoms of Eris seem similar to those of other coronavirus strains

So far, symptoms of Eris seem virtually identical to those caused by other coronavirus strains, according to Swartzberg. Eris, like other strains that cause COVID-19, can lead to a loss of taste or smell, cough, fever, chills, shortness of breath, fatigue, body aches, and headaches. Those most at risk include older people, people with compromised immune systems, and those with chronic diseases, Swartzberg said.

Eris may be more contagious than other strains, but it doesn't yet appear to be deadlier. Eris hasn't resulted in more deaths than the XBB strain of Omicron, for example.

Still, the CDC reported a 19% rise in hospitalizations from COVID-19 at the end of August compared to the previous week, and a 17.6% increase in deaths.

A new coronavirus booster could soon protect against Eris

A new coronavirus booster designed specifically to protect against XBB subvariants, like Eris, is being developed by the pharmaceutical companies Pfizer, Moderna, and Novavax. The new vaccines are expected to become available in October, and Swartzberg said they "should be very effective."

For now, experts urge people to make sure they are up-to-date on their coronavirus boosters. Only 43% of American adults over 65 are up-to-date with their COVID-19 vaccines, according to Swartzberg, and older adults are especially vulnerable to severe infection.

Additionally, people should wear N95 masks and socially distance when possible indoors.

Scientists are also eyeing another variant called Pirola

Eris isn't the only coronavirus variant that scientists are keeping an eye on. Another variant, called BA.2.86 and nicknamed "Pirola," has been recently identified by scientists.

While BA.2.86 has only been detected in a handful people globally so far, including four people in the US, the variant has a large number of mutations that could mean it is more resistant to current vaccines and natural immunity, according to the CDC in an August 23 Risk Assessment Summary.

However, the CDC said, almost the entire US population will still have some immunity through natural infection or vaccination that will still provide some protection from severe disease.

Correction: August 11, 2023 — An earlier version of the story misstated the increase in prevalence of the Eris coronavirus variant in July.