The Eris variant, formally known as EG.5, is the latest sub-lineage of the SARS-CoV-2 Omicron variant. It is a descendant of the XBB family of strains. The World Health Organization (WHO) classified EG.5 as a “Variant of Interest” due to its increasing prevalence and specific genetic changes. This classification prompted a scientific evaluation of its transmissibility and potential for severe illness compared to previous forms of the virus.
The Rise and Transmission Rate of EG.5
EG.5 has demonstrated a clear epidemiological advantage over its predecessors, quickly becoming the most prevalent circulating subvariant worldwide. Its success stems from a specific mutation on the spike protein, the part of the virus used to infect human cells. This genetic change increases the variant’s ability to evade neutralizing antibodies generated by prior infection or vaccination.
The EG.5 lineage carries the F456L mutation in its spike protein, which is a factor in its competitive edge. This mutation allows the virus to navigate better around existing immune defenses than other circulating strains, such as XBB.1.16 (Arcturus). This increased immune-evasion capability, coupled with high transmissibility, allowed EG.5 to rapidly account for a significant percentage of new COVID-19 cases.
Assessing Clinical Severity
Despite its rapid spread, the Eris variant does not appear to cause more severe disease than other recent Omicron subvariants. Surveillance data indicates that the severity of illness associated with EG.5 remains comparable to that of XBB-lineage infections. Experts have not observed evidence suggesting that EG.5 is inherently more virulent or leads to worse clinical outcomes.
While the rise of EG.5 coincided with an increase in case numbers and hospitalizations, this was primarily attributed to the variant’s higher transmissibility and waning population immunity. The overall burden on health systems remains significantly lower than during the initial waves of the pandemic. Like its close relatives, EG.5 infection typically manifests as an upper respiratory tract illness, with common symptoms including sore throat, cough, and fatigue.
Effectiveness of Current Vaccines and Immunity
The effectiveness of current vaccines and existing immunity against EG.5 involves two factors: prevention of infection and prevention of severe disease. The F456L mutation facilitates some immune evasion, meaning immunity from older vaccines or past infections is less effective at preventing mild, breakthrough infections. However, the virus remains part of the broader Omicron family, which limits the extent of this evasion.
The updated monovalent COVID-19 vaccines target the closely related XBB.1.5 lineage and produce antibodies that are cross-reactive against EG.5. This updated formulation offers robust protection against severe disease, hospitalization, and death, even if it cannot completely block all mild infections. This sustained protection is largely mediated by the body’s T-cells, which recognize parts of the virus that mutate less frequently than the spike protein. T-cells quickly destroy infected cells, preventing the virus from replicating uncontrollably and causing serious illness.
Current Public Health Recommendations
Current public health guidance is tailored to the variant’s profile of high transmissibility but moderate clinical severity. Staying up-to-date with the updated XBB-targeted monovalent vaccine is the most effective action to protect against severe outcomes. Individuals at higher risk for severe illness, such as the elderly or those with underlying health conditions, should be mindful of their vaccination status.
Maintaining basic protective behaviors remains important for slowing transmission. Anyone experiencing symptoms should stay home and utilize at-home testing to confirm an infection. Both rapid antigen tests and available antiviral treatments, such as Paxlovid, remain effective against the EG.5 variant. Individuals may also consider masking in crowded or poorly ventilated indoor settings to reduce their personal risk of exposure.