The review analyses the information on the epidemiological situation on COVID-19 around the world. Presented is the assessment of the major epidemiological parameters (basic reproductive rate, lethality, incubation period, and serial interval). Demonstrated is the share of severe cases among different age groups and the general structure of incidence by the severity of clinical course. The paper provides the classification of response models internationally depending upon the complex of measures undertaken at different stages of epidemic process. Reviewed are the key response actions to control the COVID-19 transmission in different countries of the world and the Russian Federation and given is the assessment of their effectiveness.

The review presents an analysis of epidemic and epizootic situation of Crimean-Congo hemorrhagic fever in the Russian Federation in 2010–2019, summarizes the results of epizootiological monitoring of the CCHF natural focus territory in the south of European part of Russia. An unfavorable epidemiological situation regarding CCHF is maintained in the Russian Federation. In 2010–2019, 999 CCHF cases were registered in nine regions of Southern and North-Caucasian Federal Districts. In 2019, an increase in the CCHF incidence level in the entities of the SFD and NCFD was observed as compared to 2017–2018. The expansion of the territory with registered epidemic manifestations of CCHF continues. In 2010–2019, the number of imago and pre-imaginal phases of Hyalomma marginatum – the main vector of the CCHF virus in Russia, remained consistently high. High numbers of H. marginatum ticks and their CCHFV infection rates can contribute to the development of an unfavorable epidemiological situation in the south of the Russian Federation with a possible increase in the CCHF incidence in 2020.

The review provides the data on the epidemic condition of tularemia foci in countries neighboring Russia and ongoing preventive measures in these territories. The highest tularemia incidence in the stated countries and in the world as a whole is observed in Finland. In 2019, 42 cases of human infection with tularemia pathogen were recorded in the territory of the Russian Federation, 85 % of which occur in three Federal Districts: North-Western, Central, and Siberian. Epizootic manifestations of infection of varying degrees of intensity were detected in 51 entities of the Federation. Against this background, sporadic cases of tularemia are registered in 17 regions of the country. The most severe epidemic complications continue in Karelia – 9 patients. Seventeen Francisella tularensis cultures were isolated from environmental objects in the Tver, Yaroslavl, Vologda Regions, in the Altai Territory and the Altai Republic. The paper gives an opinion on the regions in which epidemic complications of tularemia are most likely to occur in 2020.

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.

Objective of the investigation was to assess epidemiological and epizootiological conditions in natural plague foci of the Russian Federation, neighboring states and foreign countries in 2019. Negative effect of the current climate warming on the state of parasitic systems of natural foci with circulation of plague microbe of the main subspecies, medieval biovar, phylogenetic branch 2.MED1 is emphasized. In 2019, local plague epizooties were registered in the territory of two (Gorno-Altai high-mountain and Tuva mountain) out of 11 natural plague foci of the Russian Federation. The total area of epizooty covered 2248.5 km² . All in all, 31 cultures of Y. pestis of the main subspecies, antique biovar, phylogenetic branch 4.ANT and 5 cultures of Altai biovar, central-asian subspecies, phylogenetic branch 0.PE4a were isolated. The forecast for continuing tense epidemiological situation, both for 2020 and for 2021–2025, has been substantiated for natural foci with circulation of the main subspecies of antique biovar, phyologenetic branch 4.ANT: Gorno-Altai high-mountain and Tuva mountain ones. In the remaining nine natural foci in the territory of the Russian Federation epizootic manifestations of plague in 2020 are highly improbable. This prognosis is an indication to optimize the deployment of human and logistical resources of plague control institutions through concentrated preventive activities in the territories of epizootically active natural plague foci. Otlined is the necessity to put a new enhanced classification of Y. pestis into practice.

The trend towards an increase in the West Nile fever incidence among the population in the Russian Federation, recorded in the season of 2018, continued and led to a significant increase in the incidence in 2019 (the indicator was 2 times higher than the long-term average). The features of manifestations of the epidemiological process of WNF in 2019 were identified: early registration of cases of the disease, activation of natural and natural-anthropourgic foci in the Southern Federal District (90 % of the total incidence in the Russian Federation), an increase in the share of neuro-invasive forms, dominance of patients aged 50 and older in the structure of the incidence, late epidemic season ending. It was established that in the season of 2019, the lineage 2 of WNV circulated in the European part of Russia. In the Volgograd Region, simultaneous presence of the West Nile virus and Sindbis virus in mosquitoes Culex pipiens and Culex modestus was identified. It was shown that the most significant factors for predicting the epidemiological situation on West Nile fever in the Volgograd Region are the average seasonal summer air temperature and monthly average indicators of relative humidity in the spring and summer periods, and the average monthly air temperatures in the spring and summer in the Rostov Region. In the Astrakhan Region, a significant correlation dependence of the influence of the considered factors on the incidence of the population has not been established. The forecast of the development of epidemic situation in 2020 does not exclude a possible increase in the incidence in the territories of the European part of Russia, endemic for West Nile fever, and the occurrence of local outbreaks in individual constituent entities, if the complex of climatic conditions and social factors favorable for West Nile virus coincide.

Objective of the study was to analyze the incidence of Siberian tick-borne typhus (STBT) in the Russian Federation between 2010 and 2019, Astrakhan spotted fever (ASF) and Mediterranean fever (MF) since official registration, and forecast the development of the epidemic process for endemic rickettsioses for 2020. Materials and methods. The analysis of the incidence of STBT, ASF and MF in the Russian Federation over the period of 2010–2019, 2013–2019 and 2014–2019, respectively, in relation to the results of zoological-entomological monitoring. Results and discussion. The average long-term incidence rate of STBT for 2010–2019 in the Russian Federation on the whole was 1.1 ⁰ /₀₀₀₀ (DI₉₅ 1.05÷1.08) without trends towards change. The maximum relative incidence of STBT is typical for the Siberian Federal District (SFD) where the average long-term incidence rate for 2010–2019 amounted to 6.28 per 100 thousand of the population. In the second place is the Far Eastern Federal District (FEFD) – 5.17 ⁰ /₀₀₀₀, in third – the Ural Federal District (UFD) – 0.1 ⁰ /₀₀₀₀. When assessing the 10‑year dynamics of the relative incidence of STBT, we have revealed a significant tendency to increase in the FEFD, a tendency to stabilize in the SFD and a significant downward trend – in the UFD. A reliable increasing trend in STBT incidence was detected in the Altai Republic and in the Khabarovsk Territory. Major decline in STBT incidence was observed in the Trans-Baikal territory, Krasnoyarsk territory, Kurgan Region and the Republic of Khakassia. There is a marked tendency to increase in the incidence of MF in the Republic of Crimea. In the Astrakhan Region and the Republic of Kalmykia, there is an expressed tendency towards the reduction in the ASF morbidity rates.

Objective of the study was to conduct the analysis and develop the method of forecasting of viral hepatitis A (VHA) incidence using Wald’s schedule. Materials and methods. The work is based on official statistical data of the Rospotrebnadzor on the VHA morbidity rates in the Russian Federation and Moscow city between 2010 and 2016. Results and discussion. It is established that in the overall incidence of VHA cases in the Russian Federation over the period of 2010–2016, 67.7 % were registered among adults and 32.3 % – among children; as for the incidence among adults in Moscow, it accounted for 79.8 %, and for children – 20.2 %. To assess epidemiological situation on VHA, forecasting approach using Wald’s schedule was put forward. Based on the results of the analysis conducted, the threshold values for morbidity rates among adult population in Moscow stood at 38 cases, fluctuations in mean values ranged from 48 to 63 cases. It is shown that the total minimum and maximum levels of morbidity among adult population in 2017 would account for 180 and 624 cases, respectively. Forecast of incidence among children is determined on an accrual basis: minimum monthly level – 7 cases, maximum – 17. Monthly growth of infection is 0.9 cases. It is revealed that possible cumulative minimum and maximum morbidity rates among children would amount to 84 and 204 cases in 2017, respectively. The proposed method of Wald’s schedule for VHA incidence forecasting will allow for determining both monthly minimum and maximum rates of infection for the upcoming period and provide for timely planning of anti-epidemic measures.

Objective of the study was to conduct phylogenetic analysis of Yersinia pestis strains of the main subspecies, belonging to antique biovar, phylogenetic branch 0.ANT, isolated in XX – early XXI centuries in the foci of Tien-Shan and Pamir-Alay to identify the regularities of spatial-temporal circulation of plague agent in the territory of the foci. Materials and methods. We have carried out whole genome SNP-analysis of Y. pestis strains of antique biovar, isolated in natural foci of Kyrgyz Republic in 1928–2016. Phylogenetic investigation is based on 1646 identified core SNPs in 51 included in the analysis strains of different phylogenetic lines. Phylogenetic tree was constructed using Maximum Likelihood algorithm, PHYML software package, and HKY85 model. Results and discussion. All 29 studied Y. pestis strains isolated between 1928 and 2016 in the foci of Tien-Shan and Pamir-Alay fall under the phylogenetic branches 0.ANT3 and 0.ANT5 of antique biovar of the main subspecies. Strains of 0.ANT3 branch were collected predominantly in Aksay and Alay foci, while strains of 0. ANT5 – in Upper-Naryn and Sarydzhas foci of Tien-Shan. Strains of phylogenetic lines 0.ANT1 and 0.ANT2 were not found in the foci of Kyrgyz Republic. According to the results of whole genome SNP-analysis, Y. pestis strains isolated in the XXI century belong to phylogenetic branch 0.ANT5. This branch also comprises a strain obtained from a patient (lethal case) in Sarydzhas plague focus in 2013. Genetic homogeneity of the modern strains of 0.ANT5 branch and their wide dissemination testify to the extension of the areal of this population and activation of Tien-Shan foci, caused by climate warming. For the first time ever, genomes of Y. pestis 0.ANT5 branch, isolated in XXI century, including clinical strain dated 2013, have been sequenced. We have obtained the whole-genome sequence of Y. pestis strain, 0.ANT3 branch, which caused pneumonic plague outbreak in Tien-Shan in 1928.

Objective. Applying microbiological method to determine the effectiveness of disinfection treatments with formaldehyde fumigation of the hidden cavities and the reverse side of the microbiological safety cabinet filters (MSC) located in the “infectious” areas of an isolated to maximum extent laboratory. Evaluation of the effectiveness of experimental unit for automation of the formaldehyde treatment of laboratory premises. Materials and methods. Assessment of effectiveness of disinfection treatments of MSCs and the premises of virological laboratory was carried out using cambric test objects contaminated with the spore-forming test culture of B. thuringiensis. Results and discussion. The disinfection time sufficient for the complete inactivation of particularly dangerous pathogenic microorganisms potentially located in hidden cavities and on the back side of microbiological safety cabinet filters, placed in the “infectious” zone of the most isolated laboratory has been determined experimentally. As a result of the studies, it was possible to achieve complete inactivation of the spore-forming test microorganism located on test objects situated in hidden cavities and hardly accessible places of MSC at concentration of 1·10⁶ cells/cm³ only with disinfection time equal to 24 hours. Effective disinfection of test objects contaminated with B. thuringiensis spore-forming test culture, placed in hard-toreach places and on the back of the equipment in a boxed virological room, using an experimental plant producing gaseous formaldehyde, was possible only when formalin was used in a concentration of 40 ml/m³ of the room. It was established that the amount of formalin required to achieve 100% efficiency of the disinfection treatment of the virological boxed room using an experimental unit producing gaseous formaldehyde depends on the operating mode of the general supply and exhaust ventilation, the configuration of the laboratory room, and the furnishing with laboratory and engineering equipment.

HFRS is a relevant threat to the sanitary-epidemiological welfare of the population of the Russian Federation. It takes a leading position in the structure of natural-focal ifections of viral etiology incidence around the country. The most unfavorable situation on HFRS morbidity rates (more than 80% of the overall incidence) is observed in the constituent entities of the Volga Federal District (VFD). The purpose of the work is to differentiate the territory of the Volga Federal District in terms of the potential epidemic hazard (PEH) of HFRS infection. Materials and methods. We used information on the HFRS incidence contained in the statistical reporting form No. 1 “Information on infectious and parasitic diseases” and the data on epizootic activity of natural HFRS foci from the established forms of surveys and forecasts of the state of population and the numbers of small mammals over the period of 2014-2018. The assessment of the PEH level of HFRS infection was carried out according to the original method developed with the participation of the authors. The software used was the analytical platform Deductor Professional and the geo-information system Arc GIS. Results and discussion. Among the constituent entities of the Volga Federal District an extremely high level of risk of HFRS infection (6 points), the first type of territories, was established for the Udmurt Republic, the Republics of Bashkortostan, Tatarstan, Mordovia, and Chuvash Republic. The second type of territories characterized by high level of risk, where the PEH was 5 points – Samara, Ulyanovsk, Nizhny Novgorod, Kirov, Saratov, Orenburg regions and the Republic of Mari El. The territories in which there is an increased risk of HFRS infection cover the territory of the Penza Region (PEH – 4 points). The average risk of infection was noted only in the Perm Region (PEH – 3 points). Prompt implementation of a complex of nonspecific preventive measures at sites with a pronounced increase in the potential epidemic hazard of HFRS infection will significantly reduce the incidence rate in the VFD and the Russian Federation as a whole.

Aim – to determine the intensity of West Nile virus circulation in anthropogenic biotopes in the territory of the Saratov Region between 2012 and 2017. Materials and methods. 1454 blood serum samples from animals of private households and agricultural cooperatives in 14 districts of the Region were investigated: 1111 samples from horses and 343 samples from the cattle. Sera were examined for the presence of total antibodies to WNV using a test system registered in the Russian Federation to detect antibodies to this virus by a competitive enzyme immunoassay «ID Screen West Nile Competition Multi-species» («ID. Vet», France). Results and discussion. The share of resistant to WNV cohort of live-stock animals in the territory of the Saratov Region over the whole period of study was (14.0±0.9) %, particularly in horses – (15.9±1.1) %, and in the cattle – (7.9±1.5) %. The highest values were observed for horses. High level of resistance in live-stock animals was registered in the districts located on the left bank of the river Volga: central ones – Engels (36.4±5.5), Fedorovsky (29.0±4.6), and Sovetsky (20.0±3.7); southern districts – Rovensky (74.3±5.3 %) and Krasnokutsky (15.7±4.4), which confirms the assumption about the initial introduction of the virus from neighboring territories of the Volgograd Region into the territory of the Left Bank where there are characteristic near-water biotopes and active circulation of the agent takes place. The data obtained on the detection of the resistant live-stock animal cohort testify to the spread of West Nile virus in the territory of the surveyed districts of the Saratov Region and, in particular, anthropogenic biotopes which further points to the formation of persistent natural and natural-anthropourgic foci of West Nile fever.

Objective of the study was to review the current normative-methodological documentation on the matters of safe handling of pathogenic biological agents (PBA) of the III–IV pathogenicity groups. Materials and methods. We used analytical method for the study. We carried out comparative analysis of the provisions contained in the current regulations approved at different times for different agencies on the matters of air filtering system equipping, usage of microbiological safety cabinets, ensuring hand washing station provision for laboratories, inspection of disinfectants entering a lab, and waste decontamination procedures. Results and discussion. We have considered the provisions of the current documentation that require further refinement and clarification for the future editions of sanitary regulations. Two aspects draw increasing attention: the problem of regulating the inlet and exhaust ventilation system setup in the laboratories of microbiological specialization for work with PBA and the need to devise a consistent coordinated regulatory framework. Examples provided in the paper demonstrate the necessity of adhering to the integrated unified approach to the requirements for biosafety provision in the documents of various agencies; clear wording; harmonized system of normative and technical specifications for laboratory equipment, stating the basic characteristics of microbiological safety cabinets and ventilation systems. The documents should be in compliance with the requirements of various agencies. The maintenance of technical-engineering systems should be performed by the specialists with an appropriate qualification on a regular basis.

Aim. Investigation of modern epizootic and epidemic situation on West Nile fever (WNF) in the south of the European part of the Russian Federation. Materials and methods. Data from statistical documentation (epidemiological survey of the infectious disease focus, annual summary reports over the period of 2009–2018) and epizootic monitoring data presented by the Rospotrebnadzor Administrations and the Centers of Hygiene and Epidemiology in the constituent entities of the Southern and the North Caucasian Federal Districts were used. Descriptive, analytical methods and retrospective epidemiological analysis were applied. Results and discusson. The activity of natural WNF focus in the south of the European part of the Russian Federation was confirmed by the results of the annual epizootiological monitoring and the annual epidemic manifestations of the disease. 74.15 per cent of the cases and all major WNF outbreaks in the country between 2009 and 2018 were noted in the territory of the southern region. Most of the patients (97.8 per cent) are registered in the Volgograd, Astrakhan and Rostov Regions. In other southern entities sporadic incidence (this represents 2.2 per cent of all WNF cases in the south of the Russian Federation) was noted. Less serious clinical forms of the disease without the damage of central nervous system were observed in most of WNF patients. Fatal outcomes were registered in 7 WNF patients (this represents 0.58 per cent of all cases) over the past 10 years. The significant expanding of the West Nile virus geographic area and activation of the natural foci of this infection in the south of the Russian Federation in 2009- 2018 has been established. The epizootic and epidemic WNF center is located in the Volgograd, Astrakhan and Rostov Regions. It was confirmed by persistent epizootic and epidemic instability in this territory. The modern epidemic WNF feature in the south of the European part of the Russian Federation during the 10-year survey period is the relatively low mortality (0.58 per cent).

Objective is analyzing the origin of the ctxAB^– tcpA⁺ Vibrio cholerae О1 El Tor strains isolated from the surface water bodies in the territory that is non-endemic of cholera; as well as investigating their phylogenetic relations to varying by epidemic significance groups of strains, based on the structure of housekeeping genes and whole genome structure. Materials and methods: we examined 25 V. cholerae strains, isolated in Siberia and Far East, including two ctxAB^– tcpA⁺ strains from surface water sources (Altai Territory, 2011; Khabarovsk Territory, 2013). Phylogenetic analysis included genomes of 36 V. cholerae strains from GenBank. Multilocus sequence typing (MLST) was carried out based on dnaE, cat, lap, pgm, recA, gyrB, and chi genes; in silico MLST – adk, gyrB, metE, mdh, pntA, purM and pyrC genes. Reconstruction of phylogeny was performed based on the comparative analysis of core genome SNPs in PhyML 3.0. Results and discussion. MLST of ctxAB^– tcpA⁺ V. cholerae О1 El Tor strains from the surface water bodies revealed that such strains form an individual genotype in the cluster of toxigenic strains and spontaneous mutants of toxigenic strains. According to results of in silico MLST, ctxAB^– tcpA⁺ isolates belong to SТ75, common to US Gulf phylogenetic line. Based on SNP-typing, ctxAB^– tcpA⁺ strains from the surface water sources were assigned to the group, originating from US Gulf V. cholerae, moreover isolate from Khabarovsk (2013) demonstrated high degree of genome homology with US Gulf-like strain from China (2009). For strains from Khabarovsk and China, we also showed the compositional identity of the pathogenicity island VPI-I and the presence of pandemicity island, VSP-1. The results testify to the fact that ctxAB^– tcpA⁺ V. cholerae strains, isolated in Siberia and Far East, originate from the US Gulf phylogenetic line. Furthermore, taking into account the results of epidemiological analysis, we can deduce that these strains are imported ones.

Objective. The purpose of our work was molecular genetic characterization of the hepatitis D virus isolates, circulating in the region with high prevalence of HBV + HDV super-infection. Materials and methods. The study material was 64 blood serum samples obtained from Kyrgyz Republic residents - patients with chronic viral hepatitis B+D. The hepatitis D virus complete genomes were sequenced, followed by phylogenetic analysis. Results and discussion. Based on the phylogenetic analysis of 64 HDV samples, it was shown that HDV genotype 1 (96.9 %) predominates in the examined group compared with HDV genotype 2 (3.1 %). Sequences were submitted to GenBank under access No MN984407 through MN984470. When assessing the genetic variability over the examined HDV genotype 1 samples, the maximum genetic distance was 12,49 %, and the minimum – 7,41 %. Within individual clusters, the genetic distance averaged from 2.6 % to 8.5 %. Among the sequences in GenBank, the closest resemblance to the HDV-2 Kyr41 and Kyr43 samples (nucleotide identity was 92.31 % and 89.57 %, respectively) was shown for the virus described earlier in Yakutia (AJ309880). To study the genetic relationships between the analyzed HDV genotype 1 strains in comparison with the HDV reference sequences, the predicted amino acid sequence was studied (111–214). Although hepatitis B preventive measures, including vaccination, have reduced the hepatitis D incidence, there is no effective way to prevent HDV infection in HBV carriers in endemic areas. The HDV sequence molecular-genetic characterization in this study, as well as the viral genomic sequence phylogenetic analysis, will help identify pathogen transmission pathways to control and / or prevent the spread of infection.

Objective of the study is to detect circulation of plague agent and agents of other zoonotic infections (tularemia, pseudotuberculosis, leptospirosis, West Nile fever, Lassa fever, Dengue fever, Chikungunya fever, CrimeanCongo hemorrhagic fever, Q fever, Hantaviruses, tick-borne encephalitis, human monocytic ehrlichiosis, granulocytic anaplasmosis, and borreliosis) among small mammals and their ectoparasites in the territory of seven northern provinces of the Socialist Republic of Vietnam. Materials and methods. We have carried out epizootiological survey of seven northern provinces of the Socialist Republic of Vietnam (Dien Bien, Lai Chau, Lào Cai, Hà Giang, Lạng Sơn, Cao Bằng, and Quảng Ninh). Over the period of the study, 3400 trap/nights were accumulated, 179 specimens of small mammals caught, belonging to 10 species, 213 fleas of seven different species – collected, and 143 specimens of gamaside ticks falling under two species. The material gathered was investigated using enzyme immunoassay and polymerase chain reaction at the premises of mobile laboratory for monitoring and diagnostics. Results and discussion. Two-fold testing of 136 blood samples from small mammals revealed antibodies to F1 of Y. pestis in 14 (10.3 %) of them. Investigation of 158 samples of lung and kidney suspensions of small mammals showed that 22 (13.9 %) samples contained 16S rRNA of pathogenic leptospira, Leptospira spp. Analysis of 60 brain samples for the presence of Leptospira spp. revealed three (5.0 %) positive ones. 25 samples of gamaside ticks were tested for the presence of the DNA of Q fever, plague, tularemia and granulocytic anaplasmosis agents, and for the RNA of tick-borne encephalitis, human monocytic ehrlichiosis, and borreliosis agents. One sample (4 %) of gamaside ticks, Laelaps echidninus, contained RNA of Borrelia.

Of blessed memory of Natalia I. Mikshis.

Of blessed memory of Alfred S. Vasenin.