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The aim of the work was to analyze the epidemiological situation on tick-borne viral encephalitis in the endemic territories of the Russian Federation in 2021 in comparison with the dynamics over 2011–2020 and its shortterm forecast for 2022. In Russia, 48 constituent entities belonging to seven federal districts are endemic for tick-borne viral encephalitis (TBVE). There is a statistically significant downward trend in the incidence of TBVE in the Siberian Federal District (which is characterized by the maximum incidence rate in the country), the Volga and Far Eastern Federal Districts. In the Ural Federal District (the second in terms of TBVE incidence), the decline in the incidence has stalled since 2021. The average long-term incidence of TBVE in the constituent entities of the Russian Federation varies from sporadic (Republic of Crimea) up to 12.5 per 100 thousand of the population (0/0000) (Krasnoyarsk Territory). In 2021, TBVE cases were detected in 42 endemic regions and in one non-endemic region – Stavropol Territory. At the same time, 1015 cases of TBVE were in the country (0.69 0/0000). In all Federal Districts, the incidence of TBVE is below the long-term average values. Using the Quantum GIS program, the incidence of TBVE in 917 administrative territories of the country has been ranked and grouped according to the level of epidemiological risk. This made it possible to establish that 65 % of the territories form a zone of low epidemiological risk. High and very high epidemiological risk is observed in 13% of the analyzed districts. The structure of TBVE clinical manifestations in 2021 was dominated by febrile (59.7 %) and meningeal (24.3 %) forms. 14 lethal outcomes were reported. In 2021, 2 889 515 people were vaccinated (including 1 433 850 children), of which 14 fell ill. Specific immunoglobulin was used to prevent the overt development of infection in 100 704 individuals, which accounts for 22.6 % of the persons affected by tick bites (30.6 % among children). Acaricidic treatments were carried out on an operational area of 233 125 hectares of territories of socially significant objects. The scope of all TBVE prevention measures in 2021 increased as compared to 2020. In 2022, a decline in the incidence of TBVE in endemic Federal Districts and in the country on the whole is forecasted to (0,64±0,192) 0/0000.

Objective of the study was to differentiate the Administrative Districts of theTransbaikalTerritory at the time of Tick-borne viral encephalitis (TBVE) incidence recession by epidemiological risk groups and to characterize them by volume of specific and nonspecific preventive measures.Materials and methods. Retrospective analysis of TBVE epidemiological situation is based on the statistical reporting data “Information on infectious and parasitic diseases” in 2009–2019 and other materials of the Rospotrebnadzor Administration in the Transbaikal Territory. The clustering of areas with various levels of epidemiological risk was conducted by calculation of 95 % confidential interval for long-term annual average of TBVE cases in municipal units of the Territory over a decade and assessment of appurtenance of the deviating values to the aggregate under study.Results and discussion. Twenty four out of 32 districts of the Transbaikal Territory are endemic for TBVE. These areas are divided into five groups: with very high epidemiological risk (2 districts), high (5), medium (8), and low (8) risk respectively, as well as the administrative center of the constituent entity which by the whole complex of indicators (disease manifestation, population density, factors of targeted TBVE decrease, social-and-living and economical conditions) cannot be considered together with the rest of municipalities. Each group of the districts was characterized by the number of cases and TBVE incidence rates, medical aid seeking by persons who suffered from tick bites, vaccination volumes, seroprevention, areas of acaricide treatments. Recommendations are presented for the essential complex and scope of measures to prevent TBVE in the groups of administrative districts that differ by the level of epidemiological risk.

Tick-borne encephalitis is a transmissible natural-focal disease which occurs in some countries across Europe and Asia. The observation of epidemic process dynamics of TBVE in Russia covers an 80-year long period and it’s the world longest. The existence of extensive records, various data from different geographic and administrative areas opens the way to interpretation of certain ecological and social factors and their role in the regional epidemiological situation. The targeted measures against TBVE are feasible only when the role of basic predictors of decreasing incidence is defined. Objective: analysis of TBVE incidence among the population and preventive measures in the Districts and constituent entities of Russia in 2019, forecast for 2020 based on the data collected in 2010–2019. The article shows a continued downward trend in TBVE incidence, noted in recent years. However, cases of infection were registered in 6 Federal Districts and 46 regions just like in the past. The number of patients amounted to 1559 (the incidence rate is 1.02 per 100000 people), of whom 23 have died. The rate of seeking medical care among those who were bitten by ticks increased. Specific preventive measures against TBVE haven’t significantly changed by volume and focus compared to the previous period. The scope of acaricide treatments has declined. The article also presents the data concerning TBVE carriers’ infection rate, and the laboratory study results in districts and regions across the country. It is recognized that the epidemiological situation on TBVE in Russia is still unfavorable. It requires the constant attention of health facilities and Rospotrebnadzor and management decisions aimed at further decrease in the incidence by improved prevention especially in the regions with high TBVE incidence.

Studying of immune interlayer value to tick-borne encephalitis virus in human population of the Transbaikalia Territory resulted from natural immunization of the healthy population in 31 Municipal areas in 2011–2016 is presented. Human selections were formed proportionally to the population size in the concrete human settlement among persons of the various age and professional groups living at this territory not less than 10 years and unvaccinated against tick-borne encephalitis virus. Total 4367 blood sera were investigated. Laboratory testing for antibodies of G class to tick-borne encephalitis virus in blood sera of the human population was performed by immune-enzyme analysis using a set of reagents “VektoVKE-IgG” of Joint-Stock Company “Vektor-Best” (Novosibirsk city). The monitoring data indicated the presence of natural immunity to tick-borne encephalitis virus in the human population. Mean annual level of immune interlayer in Municipal areas varied from 3.1 to 52.7% (in Transbaikalian Territory — 13.1±0.51%). High level (from 20 to 52.7%) was characteristic for mountain-taiga-forest-steppe zone (Krasnochikoisky — 23.8±3.36%; Uletovsky — 52.4±4.48%; Gazimuro-Zavodsky — 29.4±4.94% districts) and mountain-tundra-taiga zone (Tungokochensky district — 20.0±3.58%). In steppe zone the level of immune interlayer was lower and observed in districts with elements of south-taiga larch and pine forests. It was established that levels of the immune interlayer in human population living in mountain-taiga-foreststeppe and mountain-tundra-taiga zones authentically higher than in steppe area — t = 3.8; Р < 0.001 and t = 2.27; Р < 0.05, respectively. Distinctions in the value of the immune interlayer between mountain-tundra-taiga and mountain-taigaforest-steppe zones were non-authentic: t = 0.1; P > 0.05. Active circulation of tick-borne encephalitis virus was accompanied by authentic (Р < 0.01) increase of the interlayer in persons with the virus antibodies in 2014–2016 (15.8±0.69%) in comparison with 2011–2013 (9.7±0.78%). Also it was noted in all landscape zones: in steppe zone the increase was to 42.8% (P > 0.05); in mountain-taiga-forest-steppe — to 61.3% (P > 0.05); in mountain-tundra-taiga — to 150.0% (Р < 0.01). It was not possible to reveal correlation between the recourse for medical aid and the value of immune interlayer in the population formed as a result of latent immunization. Results of the population immunity studying essentially expand our knowledge about the condition of the natural foci and dynamics of development of the epidemic processes in it, and can be used at planning of the preventive actions.

A complex of diagnostic measures for detection of a suspected SARS patient is analyzed. Clinical course of the disease in dynamics especially at the early stages allowed to suspect SARS in a worker arrived from China. The diagnosis was cancelled on the basis of the clinical data and laboratory negative results. However, this case allowed to practically perfect tactics of interactions between different services during realization of anti-epidemic measures in a case of SARS suspicion including notification, hospital basis development and PCR-diagnostics adoption.

We conducted regionalization of Zabaykalsky Krai by the quantity of epidemic manifestations of tick-borne viral encephalitis over a period of 10years. The most adverse territories in the context of tick-borne viral encephalitis were determined. Maximum duration of seasonal incidence rate was 112 days -from the end of April to the mid-August. The categories of population included in infection contamination risk group were revealed. The researches promote forehanded development of the complex of preventive measures aimed at the decrease of tick- borne viral encephalitis incidence rate in Zabaykalsky Krai.

Complex analysis of the data on epidemiology and clinical picture of the tick-borne borrelioses in the territory of the Trans-Baikal Region over the last decade since 2003 to 2012 has demonstrated that there is a distinct upward tendency as concerns its morbidity rates. Spotted have been the potentially hazardous, as regards the infection, areas. Highest incidence rates are registered between May-July among adult men, and erythema form of the disease prevails. Based on the results of molecular-genetic investigation of Ixodidae ticks, for the first time ever in the territory of the Dul’durginsk Region identified has been circulation of Borrelia garinii , and B. afzelii , pathogenic for humans bacterial species of Borrelia genus.

The algorithm of classification of municipal unions (MU is based on definition of a confidential interval of average long-term tick-borne encephalitis virus (TBE) sickness rate, as a quantitative integrated indicator of an epidemiological situation at the territory. It is proved that a decade is a sufficient period to reveal the patters that can be transferred to general totality and facilitate realization of MU classification. Distribution by MU groups is a steady characteristic of TBE morbidity at MU territories by decades in 95 % a confidential interval.