Ixodidae Tick-Borne Borrelioses in the World. Epidemiological Situation in the Russian Federation in 2025 in Comparison with Long-Term Data and Forecast for 2026

An overview of the epidemiological situation on Ixodidae tick-borne borreliosis (ITBB) in the world and the Russian Federation in 2025 in comparison with long-term values is presented. A forecast for 2026 is made. In 2025, the maximum number of ITBB cases was registered in the Russian Federation (9,698) over the past 15 years. Relative to the long-term average, the incidence rates of ITBB increased in 4 federal districts: Central (CFD), Volga, Southern (SFD) and North-Caucasian (NCFD) ones; the proportion of CFD in the overall structure of ITBB incidence expanded significantly (55.43 %). The number of constituent entities with a reported incidence of ITBB has risen to 84, and an increase in incidence has been noted in half of them. During the period of 2013–2025, the peculiarities of trends in the epidemic process of ITBB in territories of varying degrees of epidemiological risk persisted. In the majority of entities with a long-term average annual incidence (LTAA) above 8.4 ⁰ /₀₀₀₀, a downward trend or relative stability in the incidence of ITBB has been revealed, with the exception of Moscow and the Kaluga Region, where a pronounced upward trend was noted. In 10 out of 19 regions with LTAA between 4.2 and 8.3 ⁰ /₀₀₀₀, an upward trend was observed, while in 8 – a decrease in morbidity. The trend towards an increase in the incidence of ITBB was detected in 14 out of 24 entities with LTAA from 1.6 to 4.1 ⁰ /₀₀₀₀ and in 19 of the 29 regions with low LTAA (up to 1.5 ⁰ /₀₀₀₀). The analysis of trends in the development of the epidemic process and calculations of the probable incidence rate allows us to conclude that for most federal districts, the incidence rate of ITBB in 2026 will vary around the confidence intervals of the long-term average values, with the exception of the CFD, SFD and NCFD, where an increase in the number of cases of ITBB is probable. Effective control of the epidemic situation on ITBB is possible provided that it is maintained and enhanced. For regions such as Moscow, Saint Petersburg; Moscow, Voronezh, Lipetsk, Nizhny Novgorod, Kostroma, Ryazan, Tula, Kaluga, Bryansk, Kirov, Kursk, Orel, Tver, Tyumen, Penza and Irkutsk Regions, Altai and Trans-Baikal Territories, the Republics of Buryatia and Mordovia, constituent entities of the Southern Federal District and the North-Caucasian Federal District, increase in the volume and improvement of the quality of preventive measures, including hygienic education of the population, strengthening zoological and entomological monitoring of the activity and structure of natural foci, are required.

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