Latest COVID mutation EG.5 seems to be driving a recent surge in cases

Experts say the variant nicknamed Eris is thriving due to waning immunity and shifting baselines

Published August 8, 2023 9:00AM (EDT)

3D model of the novel Coronavirus (Getty Images)
3D model of the novel Coronavirus (Getty Images)

Although COVID-19 rates are overall still near historic lows after about seven months of decline, an increase in cases observed in recent summer months is a cause for concern for many who anticipate another spike in the fall when schools start back up. 

Ever since the COVID-19 pandemic began, there have been a long list of variants with confusing, jumbled names — from BA.5 to BQ.1 to XBB — which can feel like a bit of an alphabet soup. One of the country's prominent vaccine researchers, Dr. Peter Hotez, coined the term "Scrabble variants" to describe the ever-growing list of COVID mutations. In July, yet another was added to the list of variants to keep track of: EG.5, a descendent of the omicron strain that first emerged in November 2021. We've been dealing with omicron's children ever since.

Every two weeks, the Centers for Disease Control and Prevention (CDC) stirs through the "variant soup" and reports the largest shares of COVID variants. On Friday, August 4, CDC estimates pegged EG.5, as the top variant, contributing to 17.3% of reported cases. First identified in Indonesia, EG.5 has since spread globally. There are still many other variations of omicron circulating in the U.S., with XBB.1.5, nicknamed Kraken, accounting for 10.3% of cases and XBB.1.16, another variant nicknamed Arcturus, still making up 15.6% of cases, according to CDC data.


The reason behind the spike in cases is likely because "our natural immunity is waning," said Dr. Rajendram Rajnarayanan, of the New York Institute of Technology campus in Jonesboro, Arkansas. "Natural immunity is rendered by the previous variant that everyone had. This [variant] is slightly different than the previous one."

COVID infections have surged in the past three summers in the U.S and this year seems like no exception. The summer spike could be partially driven by record high travel rates and heatwaves sending people indoors. After President Joseph Biden and the World Health Organization declared the pandemic was over in April and May respectively, many were likely eager to take trips that had been postponed or canceled in the earlier stages of the pandemic, while many abandoned pandemic protocols altogether.

"Our natural immunity is waning. This variant is slightly different than the previous one."

This also reduced the amount of data collected on COVID transmissions available for researchers to track, Rajnarayanan said. Currently, hospitalization data, as well as wastewater monitoring, are some of the best available tools to monitor the spread of the virus. Both metrics are on the rise across the country, with CDC data on hospitalizations rising 12.5% in the past week to roughly 9,000 cases.

"After the public health emergency ended, one by one our testing and sequencing tools went away," RajnarayananI told Salon in a phone interview. "I hope the wastewater sequencing still continues, but I'm not sure how long it's going to continue either."

While the beginning surges of COVID infection rapidly increased in big waves, cases in the past year have been rising more slowly. Dr. T. Ryan Gregory, an evolutionary and genome biologist at the University of Guelph in Canada, said the increase in cases in the past year has been more like a "rising sea level" rather than "tsunami" waves.

The increase in cases in the past year has been more like a "rising sea level" rather than "tsunami" waves.

"My best guess right now is that we'll see a return to a high baseline, but not a huge wave," Gregory told Salon in an email, adding that a similar pattern was observed in Canada in spring 2022 with the BA.2 variant. 

"I think we may be returning to that situation – which also is not good, because a sustained high baseline means a lot of infections overall, which means more long COVID and more variant evolution," he said.

It's likely that some forms of EG.5, including EG.5.1, which scientists are calling Eris, will present with symptoms very similar to omicron variants, Gregory said, including headaches, sore throat and cough.

"It's very difficult to assess severity or symptoms for any particular variant these days when several are circulating at the same time and when there is so little testing," Gregory said. "The mutations that Eris has wouldn't necessarily be expected to change its severity or symptom profile relative to previously dominant XBB variants."

EG.5 descends from XBB.1.9.2, nicknamed Hyperion, which currently makes up 5.4% of cases. One of the differences between EG.5 and its immediate ancestor is that it has another spike protein mutation that effectively allows the virus to attach to receptors in cells even more easily. XBB.1.9.2 also underwent a spike mutation that distinguished it from its ancestor, Kraken. Essentially, the virus is getting more adept at finding new ways to attach itself.

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"Every time you put some kind of pressure on this virus, it learns new tricks," Rajnarayanan said.

Vaccine makers are in the process of developing new boosters specifically geared toward XBB omicron subvariants that will likely work against the EG.5 variant as well. Current vaccines will still reduce the risk of hospitalization and severe disease, but may not work as effectively to reduce the spread of newer mutations like EG.5, Rajnarayanan said.

"Every time you put some kind of pressure on this virus, it learns new tricks."

As always, following standard COVID protocols, including masking, will also help reduce the risk of infection. Staying up to date on vaccines, testing often and improving indoor air quality are all strategies that will work against the SARS-CoV-2 virus, which causes COVID, no matter how much it mutates.

"The surge is starting right now but the real surge is probably going to be happening right after Thanksgiving," Rajnarayanan said. "We want to be sure we have our boosters ready before that period."

By Elizabeth Hlavinka

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