West Nile Fever: Analysis of the Epidemiological Situation in the Russian Federation in 2023, Forecast for 2024

An analysis of the epidemiological situation on West Nile fever (WNF) in the Russian Federation in 2023 has revealed an increase in the number of cases (210) relative to the year 2022 by 6.3 times, the long-term average value by 1.2 times. Manifestations of the epidemic process were characterized by a significant expansion in the number of territories, where cases of the disease were confirmed (24 constituent entities, including in 13 – for the first time); a long epidemic season; an increase in the proportion of cases with a severe clinical course and fatality rate, which significantly exceeded the long-term average across Russia (8.5 and 1.2 %, respectively). Patients with fever and other similar manifestations of WNF were examined for the presence of the disease markers in 50 entities of the Russian Federation. Continued trend towards a decrease in the volume of diagnostic studies carried out by medical organizations and an increase in the time required for the etiological deciphering of disease cases has been established. Serological examination of sample groups of healthy population was performed in 65 entities. Epizootiological monitoring was carried out in 74 entities, rate of infection of carriers and vectors with West Nile virus (WNV) was confirmed in 14 entities. In the territory of the European part of Russia and the North Caucasus, the circulation of WNV lineages 1, 2 and 4 with the dominance of WNV lineage 2 has been established. Data on the genetic heterogeneity of WNV lineage 2 strains that circulated in Russia in 2023 have been obtained. Based on an analysis of climatic factors, a forecast of WNF incidence in the Russian Federation for 2024 was prepared.