A colorized electron microscope image shows SARS-CoV-2, indicated in yellow, emerging from the surface of cells, indicated in blue/pink. A new strain of the coronavirus called EG.5 is rapidly gaining prominence both here and across the U.S.
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Amid a summer rise of COVID-19 cases across California, a new strain of the coronavirus is rapidly gaining prominence both here and across the U.S.
According to estimates from the U.S. Centers for Disease Control and Prevention, the subvariant known as EG.5 accounted for the largest share of genomic samples nationwide in the past week, including those in the state.
As of Friday, EG.5 made up approximately 17.3% of all COVID-19 samples in the country and 16.2% in the region covering California, Hawaii, Nevada and Arizona, surpassing all other versions for the first time. This marks a significant rise from the subvariant’s 7.5% share nationally in the first week of July.
Although the growth of EG.5 has coincided with the summer COVID swell, there’s no evidence to date that the emerging strain is responsible for it — or is more virulent than its predecessors. Instead, experts pin rising metrics on factors such as waning immune protection from previous vaccines and infections, along with changes in social behavior such as increased travel and large gatherings with minimal precautions.
EG.5 is part of the omicron family, which has been driving the COVID-19 pandemic since 2021 and is a member of the XBB branch that has dominated throughout 2023.
Updated vaccines tailored to XBB are expected to arrive in October. Experts predict the genetically similar nature of the current variants will make the reformulated shots effective in reducing the risk of infection and severe illness.
EG.5 was officially added to the World Health Organization’s list of variants under monitoring on July 19 and has already been detected in 45 countries. Researchers have called it the fastest-growing lineage globally, possessing a “slightly beneficial mutation” that gives it a 50% growth advantage over other XBB subvariants. That means its proportion in the population could double every two weeks.
Symptoms linked to EG.5 infections appear to be similar to those associated with other omicron strains, according to the Zoe Health Study, an organization that tracks COVID cases in the U.K. The most common symptoms include a runny or stuffy nose, headache, fatigue, sneezing, sore throat and coughing.
The WHO said last month that there is currently “no evidence of rising cases and deaths or a change in disease severity associated with EG.5.” However, officials acknowledge that a lack of reliable data has made it more challenging to track changes in the virus’ behavior.
In the U.S., hospital admissions of people with COVID rose by 12.5% in the week ending July 29 compared with the previous seven-day period, following a steady decline since December. Emergency department visits for COVID were up nearly 22% in the same period. Similarly, England saw a 40.7% increase in hospitalizations for the week ending July 29, according to U.K. health department data.
“To be clear, we are not looking at an ‘omicron event’ now, whereby there will be a dramatic increase in transmission and adverse outcomes due to a boatload of new mutations,” wrote Eric Topol, director of the Scripps Research Translational Institute and a leading voice on COVID, in a Substack post highlighting the impact of EG.5. “But these changes in the spike of the virus… are a signal that there’s more to come with SARS-CoV-2 and we have a bad track record of always lagging behind.”
On Friday, the CDC was able to publish estimates for the proportion of variants such as EG.5 in only three regions of the country, including those surrounding New York and Georgia, due to limited data reporting.
While some reports and social media posts have unofficially referred to EG.5 as “Eris,” the WHO has revised its naming system, reserving Greek alphabet labels and nicknames solely for variants of concern like delta and omicron, not for variants under monitoring or of interest.
Reach Aidin Vaziri: avaziri@sfchronicle.com
Aidin Vaziri is a staff writer at The San Francisco Chronicle.