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COVID variant EG.5: What we know about 'eris'

Hannah Fuchs
August 16, 2023

The WHO has said new omicron subvariant EG.5 eris is a virus of interest. It's reignited talk about vaccines and speculation about a return of the pandemic.

A person wearing a mask holds up a COVID test
Come autumn/winter, we may be back to regular COVID testsImage: pressefoto_korb/picture alliance

After more than three years of the COVID-19 pandemic, the World Health Organization ended the global public health emergency on May 5, 2023.

But at the same time, WHO Director-General Tedros Adhanom Ghebreyesus noted that SARS-CoV-2, the virus that leads to COVID, had not been fully defeated, that it continued to circulate in the world and that we could still see the emergence of new and more dangerous variants.

And that's where we are now: there is a new COVID variant: EG.5, also known as eris. We just don't know yet whether it's more dangerous than previous variants.

The WHO has classified the EG.5 as a variant of interest. At time of writing, it is not a variant of concern, which is one step worse that a variant of interest.

Variants of concern are those whose characteristics have a significant influence on the spread of the virus — because of higher rates of contagion and rising infection rates, or an increase in severe cases of the illness and COVID mortality rates.  

EG.5 is one of three variants on the WHO's watchlist. The other two are XBB.1.5, which is largely circulating in Europe and the Americas, and XBB.1.16, which is predominant in Asia.

Eris is just a nickname for EG.5

T. Ryan Gregory, an Canadian evolutionary biologist based at the University of Guelph, Ontario, has studied the subtype EG.5.1 [note the added ".1" which indicates this is the first version of EG.5 — Editor's note] and posted a comment on its nickname, eris, suggesting  the nickname may lead to some confusion as we talk more and more about the variant.

Eris is also the name of one of the largest dwarf planets in our solar system, and the Greek goddess of chaos. But, noted Gregory, the nickname is unlikely to cause a big wave in itself.

How has EG.5 spread so far?

The WHO classified EG.5 as a variant of interest due to rising infection rates attributed to the variant, the fact that it spreads fast and its ability of so-called "immune escape."

EG.5 is a descendant lineage of XBB.1.9.2. It has an additional spike mutation that may explain why it can escape the human immune system's response.

That's according to the Neherlab research group, based at the University of Basel's Biozentrum, in Switzerland. In a Neherlab variant report posted at the end of June 2023, EG.5 was already described as the "fastest growing lineage with significant circulation" in the world.

The report said EG.5 "might also be a slightly beneficial mutation."

Neherlab's data suggests that EG.5 was first detected in February 2023 in Indonesia and the following month in the United States.      

EG.5 was also on the agenda of a virtual press conference hosted by the WHO on July 27, 2023. During the briefing, Maria Van Kerkhove, the WHO's technical lead for COVID-19, said "all of the variants that we are detecting that are sublineages of omicron have an increased growth rate."

That, said Van Kerkhove, "raises the point that this virus continues to circulate and it continues to change."

In its EG.5 Initial Risk Evaluation report posted on August 7, the WHO said the variant had been sequenced more than 7,350 times, with samples from 51 countries.

Most of the variant sequences were from China, with 30.6%, or 2247 sequences. Other countries listed with at least 100 sequences included the US, South Korea, Japan, Canada, Australia, Singapore, the United Kingdom, France, Portugal and Spain.

Why we still have to 'keep an eye' on COVID

At the end of July, Van Kerkhove said "[w]e aren't seeing the same level of impact in terms of hospitalizations and deaths because people are protected largely from vaccination but also from past infection, so we have some immunity that has been built up."

But she said there is a concern that "we could potentially see new variants that could be more severe and that's something we have to keep an eye out for."

As a result, warned the epidemiologists, it's important that nations continue to report COVID-related mortality rates, hospitalizations and cases requiring intensive. But in July, only a quarter of all nations provided the WHO with death rates, and only 11% of nations provided data on severe cases.

What is post-vac syndrome?

Continuing sequencing is also vital, said Van Kerkhove. "Make no mistake, the virus has not gone away," she said.

It is, however, as yet unclear whether EG.5 caused the most recent rise in COVID cases. US-based physician and scientist Eric Topol said in a post on X, formerly Twitter, that while it was important to "track the evolution" of the virus, there was "no clear [cause] and effect relationship with the current (small) increases in wastewater, cases, hospitalizations."

That was backed up by the WHO's EG.5 risk assessment on August 9.

COVID-19: The seasonal effect

Despite conclusions drawn at the time of writing, the WHO sees a potential for EG.5 to "cause a rise in case incidence and become dominant in some countries or even globally" due to its "growth advantage and immune escape characteristics" — same as it was with other variants in the omicron lineage of the virus.

Right now, though, the consensus is that EG.5 is not a big threat. The rise in cases could be explained by the fact that people in the Northern Hemisphere are in the midst of a summertime COVID wave. During the heat of summer, people tend to stay in air-conditioned spaces. As the virus continues to mutate and protections from previous infections diminishes, the risk of catching a new infection increases.

It's a good reminder to keep COVID-19 in view and under control. The latest reports suggest that updated COVID vaccines — for protection against new variants, including EG.5 — should be available in the coming months.

The updated COVID-19 booster vaccines will specifically target EG.5. But they will be based on XBB.1.5, which is also a Variant of Interest, and because it appears to be similar to EG.5, any new booster vaccines will likely provide protection against both variants.


This article was originally published in German on August 9 and has been updated to reflect various developments on August 14 and 17

This article was originally written in German.