Assessment of Population Immunity to Influenza and Acute Respiratory Viral Infections of Moscow Population during 2023–2024 Epidemic Season

Relevance . Acute respiratory viral infections (ARVI) annually occupy leading positions in terms of morbidity and economic damage both in the world and in the Russian Federation. From an epidemiological point of view, it is important to constantly monitor the circulation of influenza and ARVI viruses, as well as assess the immune structure of the population to respiratory viruses. An analysis of the features of the epidemic process of acute respiratory viral infections is necessary for further improvement of epidemiological surveillance measures for this group of infections. The aim of the study was to assess the level and prevalence of specific antibodies to various variants of the influenza virus and other relevant respiratory viruses, taking into account the epidemiological features of their circulation in Moscow during the epidemic season of 2023–2024. Materials and methods . A retrospective analysis of the incidence of influenza and acute respiratory viral infections was carried out using the form No. 2 of the Federal State Statistical Observation "Information on infectious and parasitic diseases" and data from the weekly national bulletin on influenza and Acute Respiratory Viral Infections of the Federal State Budgetary Institution "A.A. Smorodintsev Influenza Research Institute" and the Federal State Budgetary Institution "N.F. Gamalei National Research Center" of the Ministry of Health of the Russian Federation for the epidemic season 2023–2024. Molecular genetic methods (RT-PCR) were used for the etiological interpretation of disease cases and serological (ELISA, RTGA) methods to assess the level of specific antibodies (IgG) to topical pathogens of acute viral infections of the upper respiratory tract. Results and discussion . In 2024, Moscow noted an improvement in the epidemic situation for influenza and other acute respiratory viral infections compared to 2023. In the examination of 19 030 patients hospitalized at ICB No. 1 in Moscow, it was found that the proportion of influenza viruses in the structure of respiratory infections was 13.8 %, including influenza A(H3N2) – 11.8 %, A(H1N1)pdm09 – 0.5 % and B – 1.5 %. A study of the immunostructure of different groups of the city's population showed that hemagglutinating antibodies to influenza A(H3N2) virus (91.9 %) and type 3 parainfluenza (96.3%) (p > 0.05) were most often detected among children; In adults, significant differences in quantitative indicators of the immune response were found only in relation to the type 1 parainfluenza virus. The circulation of SARS-CoV-2 remained at a relatively low level during the season, with the exception of certain weeks in the summer and autumn period of 2024, when the proportion of positive samples exceeded 10 %. The total contribution of SARS-CoV-2 to the structure of acute respiratory viral infections was 13.6 %. Conclusion. A decrease in the activity of SARS-CoV-2 and a simultaneous increase in the proportion of other respiratory viruses in the SARS structure indicates a return to the pre-epidemic features of the pathogen circulation.