Features of the Epidemic Process of Enterovirus Infection in the Irkutsk Region in 2023

Introduction: Enterovirus infection is a recurring annual healthcare challenge in the Russian Federation and other countries of the world. In 2023, its incidence rate (33.9 %000) in the constituents of the Siberian Federal District was 2.7 times higher than the long-term average. Objective: To analyze the incidence of enterovirus infection in the Irkutsk Region in 2023. Materials and methods: We analyzed statistics on monthly and annual incidence of enterovirus infection in the Irkutsk Region in 2011 to 2023 and calculated long-term average monthly incidence rates and the upper limit of year-round incidence in Microsoft Excel 2013. The type of enteroviruses in patients’ clinical samples was determined by sequencing. Results: Compared to the previous year, the incidence of enterovirus infection in the Irkutsk Region in 2023 rose by 46.9 %. The main clinical form was herpangina (39.9 %), followed by hand, foot and mouth disease (HFMD) (28.9 %). Over the previous two years, most enterovirus diseases were registered in children aged 1–2 years, while the proportion of cases among children aged 7–14 years demonstrated a 1.5-fold increase (24.6 %). Enterovirus A dominated in the structure of typed enteroviruses (56.7 %), among which coxsackievirus A6 ranked first. Nucleotide sequences of human enterovirus B were obtained in 36.1 % of cases, of which ECHO30 (31.4 %) and coxsackievirus A9 (28.5 %) prevailed. Conclusion: Changes in the incidence of enterovirus infection in the Irkutsk Region observed in 2016–2019 and in the year 2023 were most likely related to the circulation of coxsackievirus A6 in the population. Importation of a new ECHO30 variant to the Irkutsk Region from other territories of the Russian Federation might have contributed to the increase in the number of cases of enterovirus meningitis.