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A retrospective descriptive epidemiological study of an incidence rate and prophylaxis of tick-borne encephalitis (TBE) was carried out in the Republic of Khakassia over 2007–2016. Also, a relative risk (RR) of the incidence rate was assessed in the cohorts of vaccinated and unvaccinated population. Over the decade, 569 TBE cases were registered. There is a distinct tendency of TBE rate reduction (slope coefficient of the regression line b = –1.1 per annum, P < 0.05) as well as an expressed irregularity in the territorial distribution of longterm average annual rates in various towns and rural districts (from 0.9 up to 44.2 cases per 100 thousand people). In the vaccinated population cohort the TBE was registered 22.8 times less than in the unvaccinated one: χ2 = 23.78 (P < 0.001); RR = 3.1 (1.9–4.9). As the extend of mass-vaccination (b = 0.06 per annum, P < 0.05) and the area of acaricide treatments (b = 0.09 per annum, P < 0.05) were increasing, the number of virus-carrying ticks was reducing (b = –0.09 per annum, P < 0.001). The results of the comparison analysis of affect to the incidence of TBEcontrollable and uncontrollable factors in the territories with various rates of incidence prove the practicability of a risk-based approach to the prophylaxis of tick-borne encephalitis.

The results of archive data analysis of the tick-borne encephalitis (TBE) cases in Irkutsk during 1995 - 2015, got from Irkutsk Regional Center for hygiene and epidemiological surveillance, are shown. During the examined period the percent of severe forms and lethal outcomes of the disease have risen. The severe forms came more often at the very beginning and at peak of ticks’ activity season. The number of alimentary TBE cases, illness of anti-TBE vaccinated persons and persons with professional risk of infection have increased in Pribaikalie during 1995 - 2015. The recurring TBE cases have been also recorded.

Division of the Asian part of the Russian Federation into southern and northern zones was implemented on the basis of physical-climatic features. The retrospective analysis of the natural focal infectious diseases in humans was carried out. Spectrum of nosological forms and epidemic process intensity in each of the evolved zones were established. Epidemic manifestations were the most expressed in the Subjects belonging to the southern zone, with domination of the Ixodes tick-borne infections. In northern zone natural focal infections included 57,1 % of local cases, they were registered only in the population of Yamal-Nenets Autonomous Okrug (District), and barely nontransmissible infections: hemorrhagic fever with renal syndrome and rabies.