Epidemiological Aspects of Outcomes of Tick-Borne Encephalitis in the North-Western Federal District

Introduction . Tick-borne encephalitis (TBE) remains one of the most significant natural focal infections in the Russia. High incidence, severe clinical course, and diverse outcomes from full recovery to persistent disability and death underscore the medical and social significance of the problem.

The aim of the study is to analyze the possible causes of high mortality in a number of regions of the Northwestern Federal District (NWFD) and assess the adequacy of existing preventive measures against TBE, as well as propose measures to improve prevention.

Materials and Methods . Data from the state statistical form No. 2 “Information on Infectious and Parasitic Diseases” for 2014–2024, demographic indicators, and annual state reports “On the State of Sanitary and Epidemiological Well-being of the Population” for NWFD territories were used. Epidemiological (descriptive-evaluative and analytical) and statistical methods were applied. Data are presented as absolute and relative values.

Results . TBE incidence in the NWFD ((1.539±0.500) per 100 000 population) consistently exceeds the national average ((1.188±0.281) per 100 000). The case fatality rate was 3.70 % (95.00 % CI 2.63–5.14). The greatest burden of fatal outcomes (45.95 %) falls on Arkhangelsk Region, where vaccination coverage does not exceed 4.00 % and acaricidal treatments cover only 0.001 % of the territory. Vologda Region reported fatalities despite vaccination coverage >11.00 %.

Discussion . Key factors associated with adverse outcomes were identified: insufficient vaccination coverage, extremely low volumes of acaricidal treatments, and poor public awareness.

Conclusion . Reducing morbidity and disability requires mass immunization in endemic territories, scaling up anti-tick treatments, and intensifying public health education.

1. Andaev EI; Nikitin AYa; Tolmacheva MI; Zarva ID; Sidorova EA; Bondaryuk AN; et al. Epidemiological situation on tick-borne viral encephalitis in the Russian Federation over the period of 2015–2024 and shortterm incidence forecast for 2025. Problems of Particularly Dangerous Infections . 2025;(1):6–17. (In Russ.). DOI: https://doi.org/10.21055/0370-1069-2025-1-6-17.

2. Nygren TM; Pilic A; Böhmer MM; Wagner-Wiening C; Wichmann O; Hellenbrand W. Recovery and sequelae in 523 adults and children with tick-borne encephalitis in Germany. Infection . 2023;51(5):1503–1511. DOI: https://doi.org/10.1007/s15010-023-02023-w.

3. Zlobin VI (ed.) Tick borne encephalitis in the 21st century . Moscow: Nauka; 2021. 471 p. (In Russ.). EDN: https://elibrary.ru/JNRXHK.

4. Ierusalimskiy AP. Tick borne encephalitis: A guide for physicians . Novosibirsk; 2001. 360 p. (In Russ.).

5. Zlobin VI; Belikov SI; Dzhioyev YuP; Demina TV; Kozlova IV. Molecular epidemiology of tick borne encephalitis . Irkutsk: RIO VSNC SO RAMN; 2003. 272 p. (In Russ.). EDN: https://elibrary.ru/PURFWP.

6. Yushchuk ND; Vengerov YuYa (eds.) Infectious diseases: National guideline . 3rd ed. Moscow: GEOTARMedia; 2021. 1104 p. (In Russ.).

7. Skripchenko NV (ed.) Neuroinfections in children . Saint Petersburg: TaktikStudio; 2015. 856 p. (In Russ.). EDN: https://elibrary.ru/VZQBTH.

8. Aksenov OA; Alekseyeva LA; Vasilyeva YuP; Vilnits AA; Govorova LV. Gorelik EYu; et al. Tick borne infections in children . Moscow: Meditsina; 2008. 422 p. (In Russ.). EDN: https://elibrary.ru/QLQXCB.

9. Skripchenko NV; Ivanova MV; Vilnits AA; Skripchenko EY. Neuroinfections in children: Trends and prospects. Russian Bulletin of Perinatology and Pediatrics . 2016;61(4):9–22. (In Russ.). DOI: https://doi.org/10.21508/1027-4065-2016-61-4-9-22.

10. Hellenbrand W; Kreusch T; Böhmer MM; Wagner-Wiening C; Dobler G; Wichmann O; et al. Epidemiology of tick-borne encephalitis (TBE) in Germany; 2001–2018. Pathogens . 2019;8(2):42. DOI: https://doi.org/10.3390/pathogens8020042.

11. Steffen R. Tick-borne encephalitis (TBE) in children in Europe: Epidemiology; clinical outcome and comparison of vaccination recommendations. Ticks and Tick Borne Diseases . 2019;10(1):100–110. DOI: https:// doi.org/10.1016/j.ttbdis.2018.08.003.

12. Kolyasnikova NM; Ishmukhametov AA; Akimkin VG. The current state of the problem of tick-borne encephalitis in Russia and the world. Epidemiology and Vaccinal Prevention . 2023;22(1):104–123. (In Russ.). https://doi.org/10.31631/2073-3046-2023-22-1-104-123.

13. Zakharycheva TA; Shirokova AS; Piotrovich IP. Long-term persistence of the tickborne encephalitis agent in the human body The Far Eastern Journal of Infectious Pathology . 2025; (49):70–73. (In Russ.). DOI: https://doi.org/10.62963/2073-2899-2025-49-70-73

14. Pashchenko GS; Popova IV; Kotsov VM; Agafonov VM. Epidemiological features and clinical picture of tickborne encephalitis in the European North of Russia. Human Ecology . 2007;(8):15–18. (In Russ.). EDN: https://elibrary.ru/IAOCKP

15. Burmagina IA; Agafonov VM; Burmagin DV. Characteristics of the emergency situation of the growth of vector-borne infections in the European North. Kazan Medical Journal . 2014;95(5):731–735. (In Russ.). EDN: https://elibrary.ru/STAJSF.

16. Titarchuk KO; Sergeeva AV; Neverova ON. Results of ecological and epidemiological monitoring of tickborne transmissive infections in the northern territories of the Arkhangelsk region in 2021‒2023. National Priorities of Russia . 2024;4(55):217–220. (In Russ.). EDN: https://elibrary.ru/FKVKSK.

17. Titarchuk KO; Solovieva YuV; Kovrov IK; Neverova ON; Dobrynina KA. Situation of incidence of infections; transmitted by ticks in the territory of Arkhangelsk Region for the period of 2018‒2020. National Priorities of Russia . 2021;3(42):282–285. (In Russ.). EDN: https://elibrary.ru/KMYTTJ.

18. Siuziumova EA; Telnova NV; Shapar AO; Aslanov BI; Stoyanova NA; Tokarevich NK. Ecological and epidemiological characteristics of tick-borne encephalitis in St. Petersburg. Russian Journal of Infection and Immunity . 2020;10(3):533–542. (In Russ.). DOI: https://doi.org/10.15789/10.15789/2220-7619-eae-924

19. Zhukova NG; Poltoratskaya TN; Sizova NN; Poltoratskaya NV; Pankina TM; Shikhin AV; et al. Tick-borne encephalitis in Tomsk region. Therapy . 2021;7(5):14–21. (In Russ.). DOI: https://doi.org/10.18565/therapy.2021.5.14–21.

20. Ruzek D; Avšič Županc T; Borde J; Chrdle A; Eyer L; Karganova GG; et al. Tick-borne encephalitis in Europe and Russia: Review of pathogenesis; clinical features; therapy; and vaccines. Antiviral Research . 2019;164:2351. DOI: https://doi.org/10.1016/j.antiviral.2019.01.014.

21. Pogodina VV; Bochkova NG; Karan LS; Frolova MP; Trukhina AG; Malenko GV; et al Comparative analysis of virulence of the Siberian and Far-East subtypes of the tick-born encephalitis virus. Problems of Virology . 2004;49(6):24–30. (In Russ.). EDN: https://elibrary.ru/OIWQWR.

22. Muminov TK; Gushchin VA; Kleymenov DA; Tkachuk AP; Manuylov VA; Siniavin AE; et al. Study of the influence of population immunity to tick-borne encephalitis virus on the characteristics of the epidemic process in Russia. Frontiers in Immunology . 2025;16:1525388. (In Russ.). DOI: https://doi.org/10.3389/fimmu.2025.1525388.

23. Liponina KA; Lukina AYu. Tick-borne viral encephalitis in the Arkhangelsk region: Epidemiological features of distribution for the period from 2015 to 2017; problems of the prehospital stage; forecast of morbidity for 2018. Bulletin of the Northern State Medical University . 2018;(1):245–247. (In Russ.). EDN: https://elibrary.ru/YOIFTV.

24. Lyapustina EE. Course of tick-borne encephalitis in the adult population of the Arkhangelsk region. Bulletin of the Northern State Medical University . 2018; (1):249–251. (In Russ.). EDN: https://elibrary.ru/YOIFUL.

25. Lai PA; Pryalochnikov SN; Isaenko SS; Malyutina TK. The incidence of tick-borne encephalitis al Journal of Humanities and Natural Sciences . 2024;(12–4):101–105. DOI: https://doi.org/10.24412/25001000-2024-12-4-101-105.