An expert from Yale Medicine explains whether EG.5 is more transmissible or more severe than previous Omicron subvariants.
As viruses mutate, it was only a matter of time before another new SARS-CoV-2 strain (the virus that causes COVID-19) emerges and starts spreading.
This summer, this strain is called EG.5, or informally Eris (nicknamed after the Greek goddess of strife and discord).
A descendant of Omicron, Eris is already the dominant coronavirus subvariant in the country, infecting more people than any other single strain.
So far, EG.5 is not raising any alarms regarding the severity of the disease, although initial reports indicate it may be more transmissible – it has overtaken XBB.1.16 (or Arcturus), another highly contagious Omicron subvariant that was in the news just before a few months.
“I am not aware of any data that suggests EG.5 leads to worse cases of COVID-19 compared to previous variants,” said Scott Roberts, MD, an infectious disease specialist at Yale Medicine.
However, initial reports have shown that EG.5 is spreading faster than any other strain currently circulating.
dr Roberts answered questions about the summer spike in COVID-19 cases and shared what we need to know about EG.5.
How common is EG.5, the newest subvariant of the coronavirus?
The Centers for Disease Control and Prevention (CDC) estimated that by the end of the third week of August, EG.5 was responsible for 20.6% of cases of COVID-19 in the United States, more than any other single circulating SARS-CoV-2 strain .
That same week, a strain called FL 1.5.1 (or Fornax), which is reported to be rapidly increasing in the US and accounted for 13.3% of cases, took second place, followed by a mix of other XBB strains and Descendants of Omicron.
How is EG.5 different from other current strains of coronavirus?
It’s not much different from other newer strains, explains Dr. Roberts. First identified in February, EG.5 is a descendant of the Omicron variant that first appeared in November 2021 and had many subvariants.
(It may be worth noting that, except in rare cases, the original version of Omicron is no longer in circulation — as are the original strain of the SARS-CoV-2 virus and the early, more severe alpha and delta variants.)
However, EG.5 has a new mutation in its spike protein (the part that facilitates entry of the virus into the host cell) that may bypass some of the immunity acquired after infection or vaccination.
“Similar to all variants that have emerged, there is some level of immune evasion due to a slight difference in genotype,” says Dr. Roberts.
The World Health Organization (WHO) has classified EG.5 as a “variant of interest,” meaning countries should monitor it more closely than other strains for mutations that could make it more contagious or serious. (The CDC has not yet updated its variant classification page.)
Is EG.5 Contributing to a Rise in COVID-19 Hospitalizations?
Most likely. This year, the CDC recorded a 14.3% uptick in COVID-related hospitalizations in the first week of August. However, this increase in cases and hospitalizations is much smaller than in previous summers.
“These summer COVID-19 spikes have been occurring over the past three years, most likely because more people are traveling,” says Dr. Roberts.
This recent increase is also likely due to the new variant, which is better at evading people’s immune systems, and the declining effectiveness of last fall’s booster shots.
Does EG.5 cause symptoms different from other subvariants of coronavirus?
Not far away. Like other Omicron strains, EG.5 tends to infect the upper respiratory tract and cause a runny nose, sore throat, and other cold-like symptoms, as opposed to lower respiratory tract symptoms, explains Dr. Roberts.
But people aged 65 or older or those with weakened immune systems have a higher risk of the virus getting into the lower respiratory tract and causing serious illness.
Will the new booster shot expected this fall protect against EG.5?
The new booster won’t exactly match EG.5 – Pfizer, Moderna, and Novavax are all developing versions targeting the Omicron offshoot XBB 1.5, a close relative.
In August, Moderna announced that early clinical studies show that the booster vaccine effectively targets both EG.5 and FL 1.5.1 subvariants.
“The two strains EG.5 and XBB.1.5 are not identical, but they are quite similar,” says Dr. Roberts. “My strong suspicion is that given the genetic similarities, there will still be good protection from the booster vaccine.
We have seen throughout the pandemic that if there is similar genetic code among the Omicron subvariants, there will be much better cross-protection – as opposed to a larger shift, as was the case from the more severe Delta variant to Omicron .”
This idea will likely be part of the basis for future seasonal COVID-19 booster shots. “The new booster this fall will not be the last,” says Dr. Roberts.
“COVID-19 is likely to be similar to the flu, with the strain mutating slightly each year, and we are developing a vaccine before we know exactly what variants will be circulating a few months later. It is always an educated guess based on the current circumstances.”
Antiviral drugs like Paxlovid should also work against EG.5, and rapid home tests should be able to detect it, adds Dr. Roberts added.
How can people protect themselves from SARS-CoV-2 and other viruses this winter?
Expectations of three viruses — SARS-CoV-2, influenza and respiratory syncytial virus (RSV) — co-emerging in the fall and winter seasons have fueled fears of a “triple disease” over the past three years.
This year there is said to be better protection from a new COVID-19 booster shot and new prevention measures against RSV, which can be fatal in vulnerable people (including infants and older adults).
This summer, the Food and Drug Administration (FDA) approved two RSV vaccines for people over 60 and a preventive monoclonal antibody for infants and young children, and recommended the CDC.
All three are expected to be available in the fall.
While the new COVID-19 boosters have yet to be approved, Dr. Roberts that anyone who receives a reformulated booster shot in the fall should expect to have adequate protection by the start of the new year – it takes around three months for the shots to reach their maximum effectiveness.
Following the pattern of previous years, Dr. Roberts expects the usual winter surge in COVID-19 cases, but hopes that given the mild form of EG.5, the availability of COVID-19 treatments such as Paxlovid and the new booster shots, there will be a far smaller surge in COVID-19 19 hospital admissions than in previous winters.
However, precautions can still be important, especially if you are at higher risk of developing a serious disease because you are 50 years of age or older, have an immunocompromised immune system, or have underlying conditions such as obesity or chronic obstructive pulmonary disease (COPD).
Protective measures such as avoiding sick people and wearing masks around people in closed spaces can help, but “the COVID-19 vaccination is the most effective means of prevention,” says Dr. Roberts.
Written by Kathy Katella.
If you are interested in Long-COVID, please read Studies on Long-COVID’s Long Mystery: It’s Not Inflammation! and Long COVID: The Uninvited Guest That Tires the Brain and Soothes the Mood.
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