Influence of the ways of spreading influenza epidemics across the territory Russia on the peculiarities of the epidemic process in various Federal districts

Aims . Show the ways of spreading influenza epidemics across the territory of Russia over a long period (1968–2019) and their influence on the incidence of influenza and ARVI in total and separately influenza A (H1N1), A (H3N2) and B in the Federal Districts in the period from 2009 to 2019. Materials and methods. The analysis of influenza epidemics was carried out according to the computer database of the National center for influenza. Results . A retrospective analysis of influenza epidemics shows the absence of inter-epidemic seasons after 1986, the increase in epidemics of mixed etiology and different routes of entry and spread of influenza viruses in Russia. During the circulation of the influenza A (H1N1)pdm09 virus, influenza epidemics were mainly of mixed etiology. The main causative agents of epidemics entered the territory of Russia more often from the west and in both ways, and from the west and from the east. In the next season, the main pathogen changed, and the path of the virus circulating in the previous season also changed. Influenza viruses of different types A and B usually diverged in time. Influenza viruses of the same type A, but of different subtypes, usually spread in different directions, with one of them having a limited distribution in the districts. The tendency of greater intensity of the epidemic process in the districts involved in the epidemic first is shown. Conclusions . 2009 to 2019 the incidence was higher in the Northwestern and Ural districts of the European part of Russia. One of the reasons for the high morbidity in these districts is the predominance of the western route of influenza viruses entering the territory of Russia and the high intensity of the epidemic process in the districts that were the first to be involved in the epidemic.