Enteroviruses as causative agents of herpangina in the population of the Russian Far East

Introduction . Enterovirus infection (EVI) is globally distributed and manifests in a wide range of clinical forms. Herpangina is one of the most frequently recorded specific manifestations of EVI. Aim . To evaluate the contribution of herpangina to the overall clinical spectrum of EVI in the Far Eastern Federal District (FEFD) and to identify the enterovirus types responsible for the disease. Materials and methods . Morbidity data for herpangina were obtained from statistical reports of Rospotrebnadzor offices in the FEFD. Enterovirus typing was performed by sequencing a fragment of the VP1 capsid-protein gene. Phylogenetic analysis was conducted using partial nucleotide sequences of Coxsackievirus A2 (CV-A2). Results . Analysis of EVI clinical forms in the FEFD from 2015 to 2024 revealed that herpangina was one of the leading manifestations, with an average proportion of 33.4%. Among 398 patients with herpangina, 92.5% were children under six years of age. Twenty-four enterovirus types were detected, predominantly CV-A10 (25.1%), CV-A6 (24.6%), CV-A5 (12.6%) and CV-A2 (7.5%). Dominant types varied by year: CV-A6 in 2015–2016, 2019 and 2023; CVA10 in 2017 and 2024; CV-A16 in 2018; CV-A5 in 2021. In several cases the virus was found in respiratory samples collected on days 5–12 of illness, indicating possible prolonged persistence of enteroviruses in the nasopharynx and contributing to the high transmissibility of herpangina. Phylogenetic analysis demonstrated genetic diversity within the CV-A2 population and concurrent circulation of lineages C and E in the FEFD during the same period. Conclusion . Herpangina constitutes a significant proportion of all recorded EVI forms in the FEFD. In most cases the causative agents are enteroviruses of species Enterovirus alphacoxsackie. Strengthened preventive measures are essential to limit transmission and prevent outbreaks.