Increased Detection of Echovirus 6-Associated Meningitis in Patients Hospitalized During the COVID-19 Pandemic, Israel 2021-2022

Background: Outbreaks of enteroviral meningitis occur periodically and may lead to hospitalizations and severe disease. Objective: To analyze and describe the meningitis outbreak in patients hospitalized in 2021-2022 during the COVID-19 pandemic. Results: In December 2021, before the emergence of the SARS-CoV-2 omicron variant, an off-season increase in enterovirus (EV) cases was observed among patients hospitalized with meningitis. One month later, Enterovirus rates decreased by 66% during the omicron wave and then increased rapidly (+78% comparing to February) after a decline in COVID-19 (March 2022). Sequencing of the Enterovirus-positive samples showed a dominance of echovirus 6 (E-6) (29%) %) before and after the Omicron wave. Phylogenetic analysis found all 29 samples are very similar and clustered in the E-6 C1 subtype. The main E-6 symptoms observed were fever and headache, along with vomiting and neck stiffness. The median patient age was 25 years, with a broad range (0-60 years). Conclusion: The upsurge in enterovirus cases was observed after the decline of the SARS-CoV-2 omicron wave. The dominant subtype was E-6, which was present before the omicron variant emergence but increased rapidly only after the omicron wave decline. We hypothesize that the omicron wave delayed the rise in E-6-associated meningitis.