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The paper considers the key areas of international activities of the Federal Service for Surveillance on Consumers’ Rights Protection and Human Well-being in strengthening cooperation with specialized agencies of foreign countries in the global provision of sanitary-epidemiological welfare of the population at the current stage. Consistent work to strengthen the international network to counter emergency situations of a sanitary and epidemiological nature through effective interaction in the field of rapid response with partner countries in the near and far abroad, including through the organization of joint scientific and practical centers for the study and prevention of infectious diseases is presented. It is shown that the programs being implemented are aimed at strengthening the national healthcare structures of partner countries to achieve independence in the implementation of monitoring and anti-epidemic measures and building a single epidemiological space, independent of the influence of global and regional geopolitical fluctuations. The relevance of increasing interstate cooperation in the field of analysis and control of biological threats, primarily infectious diseases with the potential for emergencies of a sanitary and epidemiological nature of international concern, in the South American region is considered. The currently expanding strategic biosecurity collaboration with the Bolivarian Republic of Venezuela through the establishment of the first joint research center in the South American region is described. The first results of the joint work of Russian and Venezuelan specialists are presented, confirming the successful integration of Russian experience in monitoring and preventing biological threats into the system of ensuring the sanitary and epidemiological well-being of the Venezuelan population. Promising areas for further joint research are discussed.

Ensuring the sanitary and epidemiological well-being of the population is impossible without the development of international cooperation in the field of preventing and responding to biological emergency situations. To date, a unified system of monitoring and prompt response to emergencies in the field of public health of sanitary-epidemiological nature has almost been formed in the space of the Commonwealth of Independent States (CIS). To implement legitimate interaction between the Commonwealth countries, it is necessary to develop a regulatory and methodological framework. For this purpose, the Coordination Council on the issues of sanitary protection of the territories of the member states of the Commonwealth of Independent States from the importation and spread of particularly dangerous infectious diseases has drawn a number of interstate documents, which were subsequently put into effect in the CIS. The paper presents the activities of the Coordination Council aimed at establishing and maintaining the functioning of a unified system for monitoring and prompt response to emergency situations and developing a regulatory and methodological framework that allows legitimate interaction between the Commonwealth countries.

The study presents the data on organization of laboratory testing of clinical and environmental samples within the framework of establishing the etiology of the acute intestinal infections outbreak, performed by the specialists of the joint SAET of the Rospotrebnadzor in Dolisie (Republic of the Congo) in the period of 07–24 July, 2023.Materials and methods. In order to identify the causative agents of cholera and other acute intestinal infections of bacterial and viral nature, 177 clinical and environmental samples were tested, as well as cultures on solid nutrient media and bacterial suspensions. A total of 1023 tests were carried out by polymerase chain reaction (PCR) and 305 – using bacteriological method.Results and discussion. The causative agent of cholera has not been detected in any of the samples tested. Using the PCR method, markers of acute intestinal diseases agents (Salmonella spp., Shigella spp., Campylobacter spp., Rotavirus A) have been identified in 23 clinical samples and 1 sample of bacterial suspension. No DNA/RNA of pathogens has been detected in environmental samples. During culture studies, Salmonella enterica serovar Typhi have been isolated from 8 clinical samples, and their antibiotic sensitivity has been determined. Applying whole-genome nanopore sequencing, using the MinIon platform (Oxford Nanopore Technologies, UK), nucleotide sequences of 4 S. Typhi isolates have been investigated and deposited in the international database NCBI GenBank (No. CP141260, CP141193, CP141194, CP141195). Additionally, the analysis of initially sterile samples (blood, peritoneal fluid, intraoperational samples) from the patients of General and Reference hospitals of Dolisie has resulted in the identification of 5 cultures of non-fermenting bacteria, and their antibiotic sensitivity has been determined.

The aim of the review was to assess the epidemiological situation in natural plague foci in the Russian Federation, near and far abroad countries in 2023 and to forecast their epizootic activity for 2024. In 2023, cases of plague were registered in five countries worldwide: the Democratic Republic of the Congo (60 cases), the Republic of Madagascar (14), the United States of America (2), the People’s Republic of China (3), and Mongolia (5). A total of 84 cases of plague were recorded, of which 22 (26.2 %) were fatal. In the Russian Federation, in 2023, epidemic risks in epizootically active natural foci were significantly reduced due to the implementation of a set of preventive measures carried out by Rospotrebnadzor institutions, which was the guarantor of ensuring epidemiological well-being as regards plague. Plague epizootics were detected on the territory of two (Gorno-Altai high-mountain and Tuva mountain) out of 11 natural plague foci in the Russian Federation in 2023. Epizootics were reported on the territory of the Kosh-Agach district of the Altai Republic and the Mongun-Taiginsky kozhuun of the Tuva Republic. The total area of epizootics was 731.2 km2 (in 2022 – 248.3 km2). In total, 55 cultures of the antique biovar of the main subspecies Yersinia pestis pestis were isolated in 2023 (19 in 2022). The forecast for continuation of the tense epidemiological situation in the territory of the Altai and Tuva Republics in 2024 is substantiated. The trend of sustained growth in the epizootic potential of the East Caucasus high-mountain and Dagestan plain-piedmont plague foci is outlined. The prospects for introducing an automated electronic system for assessing the epidemic potential of natural plague foci into practice are explained.

This paper provides an analysis of the results of joint work of Russian and Congolese infectious disease specialists and epidemiologists to decipher the etiology and causes of the outbreak of intestinal infections in Dolisie (Republic of the Congo) in the summer of 2023. It has been found that the increase in the incidence of intestinal infections was caused mainly by the agents of typhoid fever and dysentery; tropical malaria was a combined pathology. No cases of cholera patient detection were registered. Failure of water supply system, domestic disrepair, and low public awareness about prevention of intestinal infections contributed to the active transmission of pathogens. The combination of epidemic process manifestations testified to the aquatic nature of the outbreak. Also, cases of pathogen transmission through contact household route were recorded, food transmission was not excluded. Patients with severe and complicated forms of typhoid fever and shigellosis accounted for 50 % of those hospitalized. There was delay in seeking medical care. The available regimens of antibacterial therapy were ineffective, since there was no possibility of laboratory confirmation of the diagnosis with determination of sensitivity to drugs. Uncontrolled treatment facilitated the emergence of antibiotic resistance in pathogens, prolonged bacterial release and subsequent spread of infection. Infectious disease specialists and epidemiologists of the Rospotrebnadzor provided consulting and practical assistance to Congolese colleagues, developed and presented recommendations for optimizing anti-epidemic and therapeutic measures, taking into account the results of assessment of the causes for onset and development of the outbreak.

At present, bacteriophages are considered as an alternative to antibiotics in prevention and treatment of bacterial infections, in particular cholera.The aim of the work was to demonstrate a method to obtain synthetic bacteriophage against Vibrio cholerae. Vibriophage N4 was selected as a subject for the study.Materials and methods. The genome sequence of vibriophage N4 (38.5 kb) was taken from the NCBI GenBank database. The sequence was divided into gene blocks of 1500–2000 bp. The gene blocks, in turn, were split into oligonucleotides. Sequence partitioning was carried out using the BAC-browser software that we have developed. Oligonucleotides were chemically synthesized; gene blocks were assembled from them. After that, the complete genome of vibriophage N4 was synthesized from the obtained gene blocks. The assembly of the synthetic genome took place in two stages. At the first stage, gene block cassettes of 5–7 pieces with sizes ranging from 7 to 10.5 thousand bp were generated via homologous recombination in yeast. The resulting cassettes were then amplified and used for in vitro assembly using 5’-3’ exonuclease and thermostable DNA polymerase. The resulting preparation was used for electroporation of V. cholerae cells.Results and discussion. The synthetic genome of vibriophage N4 was delivered into the V. cholerae strain M818 O1 biovar El Tor using electroporation. As a result, the formation of lytic plaques on the lawn of V. cholerae was observed. The range of technologies we have developed: software for assembly design, enzymes and buffers for the synthesis of gene blocks and their crosslinking by homologous recombination in vitro, the method for producing large-sized assemblies in yeast can be used to obtain artificial bacteriophages with a rational genome design.

The aim of the study was to assemble full-length nucleotide sequences of the chromosome and plasmids for 13 Yersinia pestis strains from 11 natural plague foci located in the Russian Federation, using data from two sequencing technologies.Materials and methods. Y. pestis strains were grown on Hottinger’s agar (pH 7.2) at 37 °C. DNA was isolated using phenol-chloroform extraction. For the MinIon genetic analyzer (Oxford Nanopore), DNA fragments were prepared by ligation according to a modified protocol. For the Ion S5 genetic analyzer (IonTorrent), sample preparation was carried out according to the standard protocol for obtaining a library with a DNA fragment size of 400 nucleotide pairs (bp). The resulting single reads were filtered by average quality Q30 for IonTorrent and Q7 for Oxford Nanopore.Results and discussion. DNA fragments containing 50 000 or more nucleotide pairs were prepared for subsequent sequencing using nanopore sequencing technology (Oxford Nanopore). The Trycycler algorithm was applied for hybrid assembly of the genome of Y. pestis strains and correction of errors arising during this process, allowing the obtainment of full-length nucleotide sequences of the chromosome and plasmids for each genome of the strain. The nucleotide sequences of the chromosomes of 13 Y. pestis strains from 11 natural foci of plague located in the Russian Federation have been deposited in the international genetic database NCBI GenBank. It has been established that to assemble full-length genomes of Y. pestis strains, a significant number of reads with a size of 50 000 bp or more is required, and the use of the Trycycler algorithm allows one to generate a more accurate assembly of complete bacterial genomes.

The aim of the work was to study the genetic diversity and spatial-temporal structure of Yersinia pestis in the Caspian sandy plague focus using MLVA25 and CRISPR typing methods.Materials and methods. 98 Y. pestis strains isolated in the territory of the Caspian sandy plague focus in 1925–2015 were used in the study. Whole genome sequencing was performed on Ion GeneStudio S5 System (ThermoFisher Scientific) and MGI (DNBSEQ-G50RS) platforms. Fragment sequencing was conducted using “ABI PRISM 3500XL”. The search for VNTR and CRISPR loci with subsequent alignment of nucleotide sequences was carried out in the MEGA X program. The obtained sequences were entered into the created database in the Bionumerics v7.6 (Applied Maths) software. The phylogenetic tree was constructed using the UPGMA method.Results and discussion. According to the results of MLVA25 and CRISPR analysis, 98 Y. pestis strains are divided into 60 genotypes (CS1 – CS60). Variability by 23 VNTR loci has been discovered. 7 new CRISPR spacers are described: 5 in YPa and 2 in YPb (size 31–33 bp, GC composition 34–58 %). The described spacers are designated as a108, a109, a110, a111, a112, b53, b54. The interrelation of changes in the copy number of VNTR loci depending on the place and time of isolation of strains has been revealed. The data obtained can be used to carry out molecular-genetic certification of the territory of the Caspian sandy plague focus and to study the routes and patterns of evolution and spatiotemporal circulation of Y. pestis populations in the Caspian plague foci.

The circulation of a rather wide range of pathogens of natural-focal infectious diseases transmitted by ticks was detected in West Africa at different points of time: Borrelia, Rickettsia, Coxiella, Crimean-Congo hemorrhagic fever (CCHF), Bhanja, and bluetongue viruses, etc. Current epidemiological and epizootiological situation on natural-focal infectious diseases on the territory of the Republic of Guinea is not entirely clarified.The aim of this work was to identify genetic markers (RNA/DNA) of natural-focal infectious disease agents in samples of Ixodidae ticks collected in the Republic of Guinea, and to determine the spectrum of pathogens circulating in various landscape-geographical zones of the country.Materials and methods. To conduct research on the territory of all landscape-geographical zones of the Republic of Guinea, 4695 specimens of Ixodidae ticks of 11 species were collected. Taking into account the species appurtenance, gender, phase of development, as well as the site of collection, a panel of 1645 samples was compiled. Genetic markers of Crimean-Congo hemorrhagic fever and tick-borne encephalitis viruses, as well as Borrelia burgdorferi s.l., Ehrlichia chaffeensis, Ehrlichia muris, Anaplasma phagocytophilum, Coxiella burnetii, Rickettsia of the tick-borne spotted fever (TBSF) group, and Francisella tularensis were detected using polymerase chain reaction (PCR) and reverse transcription polymerase chain reaction (RT-PCR).Results and discussion. The following markers of natural-focal disease agents were found in the Ixodidae tick suspensions: DNA of Rickettsia of the TBSF group (25.6 % of all samples studied), DNA of C. burnetii (6.2 %), cDNA of B. burgdorferi s.l. (9.1 %), and RNA of the CCHF virus (2.5 %). The listed spectrum of pathogens has been registered in all landscape-geographical zones of Guinea. Genetic markers of tularemia, anaplasmosis, ehrlichiosis and tick-borne encephalitis pathogens have not been identified in this study. The results obtained made it possible to clarify the probable spectrum of tick-borne diseases in the territory of the Republic of Guinea, determined the need for further study of the circulation of natural-focal infectious disease agents in West Africa and conducting regular epizootiological monitoring.

The aim of the work was to analyze the results of investigating the field material obtained from natural plague foci of the Kyrgyz Republic (KR) in 2023, using modern diagnostic technologies.Materials and methods. 1435 biological samples from the Tien Shan, Alai and Talas high-mountain foci of the Kyrgyz Republic were studied using conventional methods of laboratory diagnosis of plague: microbiological, immunological, biological; as well as modern molecular-genetic methods. Testing of the obtained samples for the presence of plague pathogen DNA was carried out using RT-PCR; and the presence of antibodies to the plague microbe was detected by enzyme-linked immunosorbent assay (ELISA). Molecular identification of Yersinia pestis strains according to their appurtenance to subspecies, biovars, and phylogenetic lineages was performed by RT-PCR using the method of identifying single-nucleotide substitutions based on the analysis of melting curves of products.Results and discussion. An approach to the molecular identification of Y. pestis strains from plague foci of the KR has been developed and validated through identifying singlenucleotide substitutions using the analysis of product melting curves (HMR-analysis) with a set of designed primers. It has been established that Y. pestis strains isolated in the Sarydzhaz autonomous focus of the Tien Shan high-mountain focus belong to the biovar antiqua of the main subspecies, phylogenetic branch 0.ANT5. The phylogenetic relation of Y. pestis strains isolated in 2023 was studied based on genome-wide SNP analysis. Areas of epizootic activity in Eastern Alai have been identified. The data obtained indicate the sustained activation of plague foci in the KR. Areas of the territory of the KR that are promising for paleogenomic research are also discussed.

The aim of the work was to study the growth dependence on amino acids in Yersinia pestis strains of different phylogenetic branches of the antiqua biovar and to determine the genetic basis of auxotrophy of these strains.Materials and methods. We used 38 strains of Y. pestis, the main subspecies of the antiqua biovar, isolated in various foci of the world in the period of 1928–2020. The nutritional requirements of the strains were determined by incubation on Difco minimal agar with different sets of amino acids. Phylogenetic analysis of the strains was carried out using the Wombac 2.0 and SeaView 5.0.5 programs. Comparative analysis of the nucleotide sequences of the genes was performed using the BLAST algorithm and the Mega 7.0 program.Results and discussion. The phylogenetic appurtenance of the investigated Y. pestis strains of antiqua biovar to the phylogenetic branches 0.ANT3, 0.ANT5, 1.ANT, 2.ANT3, 3.ANT2, 4.ANT has been determined. It is established that all studied strains have a common dependence of growth on three amino acids – phenylalanine, threonine, and methionine. In the majority of the strains of antiqua biovar of all phylogenetic branches, growth is also dependent on the presence of cysteine in the medium, except for a part of the strains of the phylogenetic branch 4.ANT. In 14 genes of sulfur and cysteine metabolism, 19 mutations have been identified. Each phylogenetic group of the antique biovar has a distinct profile of mutations in genes involved in cysteine biosynthesis. The leucine requirement of the strains belonging to phylogenetic branch 0.ANT5 has been established, possibly caused by a frame shift in the leuA gene. Strains of the 1.ANT branch isolated in the Democratic Republic of the Congo demonstrate an additional proline-dependent growth. The defined nutritional requirements in the strains and the genetic causes of auxotrophy complement the phenotypic and genetic characteristics of the phylogenetic branches of the antiqua biovar and can be used as genetic markers for the differentiation of these strains.

Sanitary and quarantine control (SQC) at the state border of the Russian Federation is the first barrier to the importation and subsequent spread of diseases on the territory of the country. Every year the number of registered outbreaks of infectious diseases in the countries of the world increases, which entails an increase in published information, some of which is unreliable and requires verification. At the same time, against the background of the development of international tourism, increase in passenger traffic, the risk of infectious diseases importation into the territory of Russia rises manifold, which creates the need for modernization of information and technical support of the SQC. In connection with the above, the aim of the work was to develop a scientifically substantiated system of informatization and digitalization of SQC, which resulted in the introduction of an automated risk assessment system as regards importation of dangerous infectious diseases (AIS “Perimeter”) at all sanitary-quarantine checkpoints (SQP). Materials and methods. The information system was created using the following software platforms: Laravel, VueJs. The official websites of the Ministries of Health of the respective countries, data from the official regional websites of WHO, regional centers for disease control and prevention (CDC), and data from the ProMED-mail system were used as sources of information on infectious morbidity in the countries of the world. Results and discussion. Implementation of AIS “Perimeter” has brought about the maximum possible efficiency in the targeted informing of SQP officials about the current epidemiological situation in the countries of the world; an effective tool for monitoring the situation at the federal level in real-time mode. It facilitates the work of SQP, staff related to conducting standard operational procedures, due to considerable decrease in the volume of routine activities to keep records. The proposed in the AIS expert risk assessment as regards importation of infectious diseases allows SQP employees, based on reliable information, to make timely decisions on the need to conduct SQC and exclude erroneous actions in the essential set of measures within the framework of SQC implementation, while minimizing subjectivity with respect to decision making.

The review contains information on paleogenomic studies of the plague pathogen, Yersinia pestis, covering the prehistoric epoch, the periods of the first and second plague pandemics, epidemics and outbreaks of plague of the late XIX–XX centuries. We have summarized the data on the reconstruction of ancient Y. pestis genomes of the Late Neolithic, Bronze and Iron Ages, the Justinian Plague epidemic of the first plague pandemic, the Black Death epidemic and the subsequent epidemics of the second plague pandemic of the XIV–XVIII centuries, as well as on tracing the pathways of plague propagation waves in Eurasia and the course of plague agent evolution with the formation of a vector-borne transmission route with the help of arthropods. We present the results of our own research of Y. pestis genomes from the key sites of formation of etiological agents of the first and second plague pandemics in the Tien Shan Mountains, historical outbreaks in the Northern and North-Western Caspian sea region and other regions of Russia and adjoining countries in the late XIX–XX centuries. The paper discusses the areas of the Caucasus, Crimea, Northern Caspian, Siberia, and Tien Shan in the territory of Russia and neighboring states that are promising for national paleogenomic studies of plague.

The paper presents a hypothesis that the most probable cause of death of the ancient world Indus (Harappa) civilization was the epidemic of Asiatic cholera. A brief description of the Indus civilization that existed for two millennia (3300–1300 BC) is given. It is shown that the previously described factors for the decline of the thriving Indus civilization (climate change, shallowing of the Indus river and reduction in floods, catastrophic floods, drought, economic crisis, etc.) do not provide a consistent and comprehensive explanation of the causes of its death. Meanwhile, the natural environment and peculiarities of agriculture of the Indus civilization (annual floods affecting not only fields, but also sewage systems) created ideal conditions for the spread of water-borne cholera. The evolution of the Asiatic cholera agent is discussed. The results of paleogenomics study of this pathogen and their significance for the reconstruction of evolutionary events are briefly reviewed. The stages of evolution of Vibrio cholerae of the classical biovar are described, and possible mechanisms for the preservation of the pathogen during inter-epidemic period are considered. It is demonstrated that aside from cholera, other catastrophic, destructive epidemics are recorded in the history of mankind.

The aim of the work was to study interaction of Yersinia pestis with soil nematodes isolated on the territory of the Gorno-Altai high-mountain plague focus. Materials and methods. We used the fluorescent Y. pestis strain KM2083, a derivative of the natural strain of the 4.ANT phylogenetic line, the antique biovar of the main subspecies, and a nematode culture isolated in the same area of the Gorno-Altai plague focus. The taxonomy of nematodes was determined by the region of the 18S rRNA gene; phylogenetic analysis was performed using the Maximum Likelihood method based on the Tamura-Nei model in the Mega 7.0 software. The interaction of the Y. pestis KM2083 strain and the nematodes was studied during cultivation on a solid NGM agar medium. Nematodes were observed using microscopes Stemi-2000C (Carl Zeiss, Germany) and Axio Imager Z2 (Carl Zeiss, Germany). Results and discussion. It has been established that the nematodes from the Gorno-Altai high-mountain plague focus used in the work belong to the genus Panagrolaimus. Cultivation of nematodes on the lawn of the Y. pestis strain of the main subspecies of antique biovar, the 4.ANT phylogenetic line for 24 hours did not lead to a reduction in the lifespan of nematodes compared to the control sample, which indicates the absence of toxicity of the used strain towards Panagrolaimus nematodes. On the cuticle of nematodes, the formation of a biofilm in the genital area and tail has been noted, and accumulations of fluorescent cells of the plague pathogen observed in the digestive tract. The data obtained can indicate the ability of nematodes to carry the plague pathogen in the soil biocoenosis.

The paper describes a developed comprehensive system for molecular-genetic identification of Yersinia pestis strains according to their appurtenance to certain subspecies, biovars, phylo-geographic populations, using realtime PCR (RT-PCR), allele-specific RT-PCR, and multiplex PCR with hybridization fluorescent registration of results on a solid substrate. Application of this system makes it possible to establish the appurtenance of Y. pestis strains to the following phylogenetic branches: 0.ANT1, 0.ANT2, 0.ANT3, 0.ANT5, 3.ANT, 4.ANT of antique biovar of the main subspecies; 2.MED0, 2.MED1, 2.MED2, 2.MED3, 2.MED4 of medieval biovar of the main subspecies; 1.IN1, 1.IN2, 1.IN3 of intermedium biovar of the main subspecies; 1.ORI1, 1.ORI2, 1.ORI3 of oriental biovar of the main subspecies; 0.PE3 (angolica subspecies), 0.PE7 (tibetica subspecies) and 0.PE10 (qinghaica subspecies). The first stage of the studies within the frames of the developed system is indication of plague agent using registered diagnostic drugs. The second stage is the determination of belonging to individual subspecies through RT-PCR or by the method of multiplex PCR system with hybridization-fluorescent registration of results on a solid substrate, which also allows for establishing to which biovars of the main subspecies and the main phylogenetic lines of the ancient biovar the strains belong. The third stage is the identification of strain appurtenance to phylogenetic branches by the AS-RT-PCR method. The designed complex system for molecular-genetic identification of Y. pestis strains can be applied at the regional and federal levels of the laboratory network of the Russian Federation for diagnostics of infectious diseases. Its use will considerably facilitate and increase the efficiency of intraspecific differentiation of Y. pestis strains within the framework of the epidemiological investigation of outbreaks or importation of strains of plague pathogen into the territory of the Russian Federation or during the certification of strains in collection activities.

The aim of the study was to develop methodological approaches to assessing the economic damage associated with the incidence of hemorrhagic fever with renal syndrome (HFRS) and to calculate the economic damage by the example of an outbreak of HFRS in the Saratov region in 2019. Materials and methods. The paper analyzes the economic indicators of the Federal State Statistics Service; data on the incidence of HFRS in the Russian Federation for the period of 2019–2022. To calculate the cost of outpatient and inpatient medical care, as well as the costs associated with the medical follow-up of convalescents, the indicators of the Program of state guarantees of free provision of medical care to citizens for 2022 and for the scheduled period of 2023 and 2024 were used. The calculation of economic losses associated with the payment of temporary disability benefits was carried out according to the equation provided in the Federal Law No. 255-FZ dated December 29, 2006 (as amended on October 07, 2022). Economic losses associated with premature death at an economically active age were calculated based on the value of unproduced GDP due to lost years of life in the corresponding age group. Results and discussion. The costs of treatment, rehabilitation and payment of temporary disability benefits for 1 case of HFRS at the age of 0 to 56.5 years for the female population and from 0 to 61.5 years for the male population amount to 140 495 rubles; over the age of 56.5 years for the female population and 61.5 years for the male population – 95 412 rubles, respectively. Each fatal case of HFRS aged 0 to 16 years among the male population costs the state 38 976 231 rubles; among the female population – 34 708 331 rubles; in active working age – the value of economic damage varies depending on the age of the person who died of HFRS. The economic damage of the outbreak of HFRS in the Saratov Region (2019), taking into account the direct expenditures of the healthcare system and indirect losses of the country’s economy amounted to 441 453 432 rubles. It is of note that the structure of the main damage is dominated by indirect losses in the economy caused by the premature death of people in economically active age.

The aim of the work was to assess the epidemic situation on plague in the world and epizootic activity of natural plague foci of the Russian Federation in 2022. Following the implementation of comprehensive preventive interventions plans, there was a decrease in the epizootic activity of the Gorno-Altai high-mountain and Tuva mountain natural foci, the cessation of plague epizootics in the Central Caucasian high-mountain focus. The total area of epizootics in the Russian Federation in 2022 reached 248.3 km2, which is 7 times less than in 2021. Infected animals were not found in the Tersko-Sunzhensky low-mountain, Dagestan plain-piedmont, Caspian North-Western steppe, Volga-Ural steppe, Trans-Baikal steppe, Volga-Ural sandy, Caspian sandy, East Caucasian high-mountain natural foci. Persistence of tense epizootiological situation in 2023 is predicted for the territory of the Altai Republic and the Republic of Tuva. The prospects of using the GIS portal of the Russian Anti-Plague Institute “Microbe” of the Rospotrebnadzor for an operational assessment of the actual epidemiological situation in natural plague foci are substantiated.

The aim of the study was to compare the nucleotide sequences of pgm‑region genes in Yersinia pestis strains isolated on the territory of the Caspian sandy and adjacent plague foci in 1925–2015. Materials and methods. 65 Y. pestis strains from the Caspian sandy and adjacent plague foci were used in the work. DNA isolation was performed using the PureLink Genomic DNA Mini Kit. Whole genome sequencing was conducted in Ion S5 XL System (Thermo Fischer Scientific). Data processing was carried out using Ion Torrent Suite software package 3.4.2 and NewblerGS Assembler 2.6. To compare the obtained sequences with the NCBI GenBank database, the Blast algorithm was used. The phylogenetic analysis was performed according to the data of whole genome SNP analysis based on 1183 identified SNPs. The search for marker SNPs was performed using the Snippy 4.6 program. The phylogenetic tree was constructed using the Maximum Likelihood algorithm, the GTR nucleotide substitution model. Results and discussion. The nucleotide sequences of pgm‑region genes of 65 Y. pestis strains from the Caspian sandy and adjacent plague foci have been assessed. Single nucleotide substitutions have been identified in Y. pestis strains from the Caspian sandy and Kobystan plain-foothill foci in the hmsR, astB, ybtS, ypo1944, ypo1943, ypo1936 genes, as well as a deletion of 5 bp in the ypo1945 gene, which is characteristic of strains of one of the phylogenetic lines of Y. pestis from the foci of Caucasus and Transcaucasia, isolated in 1968–2001. The data obtained can be used to differentiate Y. pestis strains from the Caspian sandy focus, as well as to establish the directions of microevolution of the plague pathogen in this region and adjacent foci.

The review presents the data on domestic and foreign phenotypic classifications of Yersinia pestis strains developed in the XX century; genetic classifications of the XXI century; as well as on the genealogy of ancient strains of the plague microbe, reconstructed using paleogenomic technologies. Since the discovery of the plague agent in 1894, many classifications were created that corresponded to the level of development of microbiology at that time. The intraspecific classification schemes of the XX century were based on three principles: phenotypic differences between strains, features of the species composition of carriers, and geographical affiliation. With the development of molecular microbiology early on in the XXI century, a genetic nomenclature of the branches of the pathogen evolution was developed and a number of classifications based on the analysis of the population structure of Y. pestis were created. Through the prism of the genetic diversity of Y. pestis strains from natural plague foci in Russia, near and far abroad countries, an improved classification with a division into seven subspecies has been developed: pestis, tibetica, caucasica, qinghaica, angolica, central asiatica, ulegeica, which allocates the subspecies according to the phylogenetic principle and epidemic significance. With the advancements in paleomicrobiology, prehistoric lineages of evolution have been included in the genealogy of Y. pestis, which expand the data on the intraspecific diversity of the plague microbe.

The aim of the study was to test the feasibility of long-term survival and preservation of the properties of Yersinia pestis in association with soil amoeba Acanthamoeba castellanii. Materials and methods. Y. pestis strains and acanthamoeba isolated in the common area of the Gorno-Altai high-mountain plague focus were used for the study. The systematic affiliation of protozoa was determined through analyzing the 18S rRNA gene fragment sequencing data, followed by alignment with amoeba sequences from the NCBI GenBank database. A fluorescent Y. pestis strain was obtained by electroporation using the pTurboGFP-B plasmid. Co-cultivation was carried out in saline buffer in the absence of nutrients for the cells of plague pathogen. The influence of co-culturing with protozoa on Y. pestis properties was determined using microbiological, biological, and molecular-genetic methods. Results and discussion. The cell viability preservation for 22 months of the experiment in Y. pestis strain belonging to the main subspecies of the antique biovar, the 4.ANT phylogenetic line in co-culture with amoeba cells in the absence of additional nutrients has been established. Co-cultivation with amoebae did not lead to a change in the cultural, morphological, genetic and virulent properties of the plague pathogen strain. The data obtained confirm the possibility of using Acanthamoeba castellanii by the plague microbe to persist in soil biocenoses and open up the prospect of studying the mechanisms of plague pathogen surviving during extended inter-epizootic periods.

The SNP-typing method based on the detection of stable genetic markers in the genome, i.e., single nucleotide polymorphisms, is successfully used for genotyping of pathogenic microorganisms and can be applied for SNP-profiling of Yersinia pestis strains and molecular-genetic certification of focal areas. The aim of the study was to determine the SNP profiles of Y. pestis strains of the medieval biovar isolated in the Caspian Sea region plague foci in 1912–2015 and to develop a method for identifying unique SNPs using the Sanger sequencing for molecular-genetic certification of these territories. Materials and methods. A comprehensive study of the phenotypic and genotypic properties of 190 Y. pestis strains from plague foci in the Caspian Sea region was carried out. Phylogenetic reconstruction by the Maximum Likelihood method (GTR model) in the SeaView 5.0.4 software was performed on the basis of 1621 SNPs identified among 50 Y. pestis strains according to WG-SNP analysis in the snippy 4.6 program. Primers for PCR amplification of the SNP loci selected as target were calculated using the Vector NTI program. Sanger sequencing of SNPs loci was conducted on an ABI PRISM 3500XL genetic analyzer (Applied Biosystems, USA). Results and discussion. According to phenotypic characteristics, all studied strains from the Caspian foci belonged to a highly virulent and epidemically significant medieval biovar of the main subspecies of Y. pestis. According to the results of the WG-SNP analysis, 9 SNP genotypes were identified based on the polymorphism of single nucleotides of 24 genes characteristic of the main phylopopulations, which include strains isolated during various periods of epidemic and epizootic activity in the Caspian plague foci. Determining of SNP genotypes of Y. pestis strains of the medieval biovar, obtained over a hundred years in the Caspian foci, creates the prerequisites for defining the canonical SNP profile (canSNP) and for developing an algorithm for molecular epidemiological monitoring of the foci in which this highly virulent biovar circulates.

The paper contains the data on international cooperation of the Republican Center of Quarantine and Particularly Dangerous Infections of the Ministry of Health of the Kyrgyz Republic and the Russian Research Anti-Plague Institute “Microbe” of the Rospotrebnadzor to combat plague and other dangerous infections over the period from 2016 to 2022. Areas of cooperation include conducting joint epidemiological monitoring of plague foci in the Kyrgyz Republic; exchange of up-to-date information on the state of natural foci of the two countries; equipping the anti-plague service of the Republic with modern equipment and mobile laboratories, diagnostic tools and technologies; conducting joint exercises to ensure biological safety and prompt response to emergencies; provision of advisory and methodological assistance; training and strengthening of professional personnel; conducting joint scientific researches, conferences; publication of scientific works. Data on the complex characterization of properties and phylogeographic analysis of Yersinia pestis strains isolated during field studies in the Kyrgyz Republic in 2012–2020 are summarized. The prospects for carrying out joint cartographic, molecular-genetic and paleomicrobiological work in the natural foci of the Kyrgyz Republic are outlined.

The purpose of the work was to analyze the phylogenetic relations and origin of Yersinia pestis strains isolated in different periods of epizootic activity of the Caspian sandy natural focus (CSNF) of plague in the XX–XXI centuries.Materials and methods. We used 40 Y. pestis strains from CSNF and adjacent plague foci, isolated in 1922–2015. Carried out was whole genome sequencing of 19 Y. pestis strains from CSNF. Phylogenetic analysis was performed using whole genome SNP analysis based on 1914 identified SNPs. The search for marker SNPs was conducted using the Snippy 4.6 software. The phylogenetic tree was constructed using the Maximum Likelihood algorithm, the GTR nucleotide substitution model.Results and discussion. The whole genome SNP analysis has revealed that Y. pestis strains of the medieval biovar from CSNF belong to 2.MED1 phylogenetic lineage and fall into two major branches. One of them circulated in the focus in the first half of the XX century, and the other – in the second half of the XX – early XXI centuries. It is shown that strains of the first branch were the cause of outbreaks and individual cases of plague in the CSNF in the first half of the XX century. They are closely related to strains from the Caspian North-Western steppe and Volga-Ural sandy natural plague foci, which caused numerous outbreaks with high mortality rate in the same period. Y. pestis strains from the CSNF of the second half of the XX and early XXI centuries belong to the second phylogenetic branch of the 2.MED1 line, at the node of which the strains from the Northern Aral Sea region of 1945 lay. The latter were the predecessors of all strains isolated in the CSNF after a long inter-epizootic period that occurred in the middle of the XX century. There can also be traced a genetic relation between the strains from CSNF and the Dagestan plain-foothill focus.

The most important component of strengthening the potential for responding to biological threats both at the national and interstate levels is the formation of a unified system for monitoring and responding to emergencies (ES) of sanitary-epidemiological nature in the CIS territory.The aim of the work was to review the systems for monitoring and responding to emergencies of sanitary-epidemiological character in the CIS countries by the example of the Russian Federation, the Republic of Belarus, the Republic of Kazakhstan and the Kyrgyz Republic, to characterize the main areas of international cooperation on countering biological threats and coordinating international response measures in the CIS countries.Materials and methods. Information and analytical materials provided by organizations responsible for epidemiological surveillance and control in the CIS countries, Internet sources, and publications were used for the study.Results and discussion. The organization and functioning of the systems for monitoring and responding to emergencies in the CIS countries is a state function. It includes, as a rule, the national, regional (sub-national) and territorial (local) levels, which have horizontal and vertical connections. The legal framework is made up of documents of the legislative level. Interdepartmental interaction in response to emergencies is carried out both at the republican level and in administrative territories; the basis for interaction is the integrated planning of preventive and anti-epidemic measures and the functioning of the relevant organizational structures on an ongoing basis. Since 2015, with the support of the Government of the Russian Federation, programs have been implemented aimed at assisting partner countries in the implementation of the International Health Regulations (2005) in order to increase national response capacity and form a unified sanitaryepidemiological emergency response system in the CIS countries. The main areas of collaboration are strengthening the material and technical base and human resources of specialized institutions and scientific cooperation. As a result of the program implementation, a unified system for monitoring and prompt response to emergencies in the field of public health of sanitary-epidemiological nature has essentially been formed in the CIS countries to date, uniting more than 15 specialized institutions from 8 CIS countries.

Background. The ongoing pandemic of a new coronavirus infection (COVID-19) determines the relevance of the analysis of epidemiological patterns of SARS-CoV-2 spread among the population of the Russian Federation.Aim — study of the manifestations of the epidemic process of COVID-19 in the Russian Federation in 2020–2022.Materials and methods. A retrospective epidemiological analysis of the incidence of COVID-19 in the Russian Federation was carried out from 03/30/2020 to 04/24/2022. The data from the Rospotrebnadzor report No. 970 “Information on cases of infectious diseases in persons with suspected new coronavirus infection”, information portal Stopcoronavirus.rf, etc. were used. The presence of SARS-CoV-2 RNA was confirmed by real-time RT-PCR.Results and discussion. The analysis of the manifestations of the epidemic process of COVID-19 in the Russian Federation in 2020–2022 showed the presence of two stages which differed depending on the influence of the biological factor and the ongoing anti-epidemic measures. There was a pronounced trend in the development of the epidemic process, starting from megacities (Moscow, Moscow region and St. Petersburg), which are major transport hubs and centers of migration activity of the population, to the regions of the Russian Federation. The SARS-CoV-2 pathogenicity has been shown to decrease with each subsequent cycle of the rise in the incidence of COVID-19 against the background of the increased contagiousness of the virus.Conclusion. As a result of the study, risk areas (megacities) and risk groups were identified.

The most common anthropozoonoses on the African continent are coxiellosis and Rift Valley fever. It is known that detection of specific IgG antibodies in the blood sera of farm animals is one of the indicators of the pathogen circulation in a certain territory. The aim of the work was to identify specific IgG antibodies in the blood sera of farm animals collected on the territory of the Republic of Guinea to pathogens of zoonotic infectious diseases: coxiellosis, brucellosis, glanders, CCHF, West Nile and Rift Valley fevers, using enzyme immunoassay (ELISA). Materials and methods. A panel of 970 samples of blood sera from farm animals inhabiting all landscape-geographical zones of Guinea was compiled for the work. Identification of specific antibodies was carried out using enzyme immunoassay with preparations recommended for veterinary studies. Results and discussion. Specific antibodies to zoonoses were detected in 700 out of 1074 samples (65.2 % of the total), including: to Coxiella burnetii – in 172 (16.0 %); to Brucella spp. – in 212 (19.7 %); viruses of Rift Valley fever – 85 (7.9 %); CCHF – in 139 (12.9 %) and West Nile fever – in 92 (8.6 %). Antibodies to Burkholderia mallei were not found in the tested material. Positive samples were registered in all landscape-geographical zones. Thus, an urgent task is to continue studying the circulation of pathogens of zoonoses and anthropozoonoses in the territory of the Republic of Guinea and to organize regular monitoring over the spread of zoonotic infectious diseases in collaboration with veterinary services, which will allow timely forecasting and coordinating prophylactic (anti-epidemic) measures to prevent cases of diseases.

A comprehensive analysis of the accumulated epidemiological and epizootiological data in combination with results from phylogenetic analysis of Yersinia pestis strains creates the basis for establishing patterns of spatialtemporal distribution of the plague pathogen and opens up the prospect of long-term forecasting of natural plague foci activation. Previously, we traced the distribution pathways of Y. pestis, medieval biovar, in the plague foci of the Northern and Northwestern Caspian Sea regions in the 20th and early 21st centuries.The purpose of this work was to identify the regularities of circulation of Y. pestis, medieval biovar, in four natural plague foci located in the Eastern Caspian Sea region.Materials and methods. A complex study of the phenotypic and genetic properties of 16 Y. pestis strains isolated in the Ustyurt, Mangyshlak, Karakum and Kopetdag autonomous desert plague foci in 1926–1985 was carried out. They were compared with strains from other natural plague foci in Eastern Europe and Central Asia obtained in 1917–2003. Whole-genome sequencing of 12 of those strains was performed. Phylogenetic analysis included the genomes of other 19 Y. pestis strains that we had sequenced earlier. Based on the 1717 polymorphic nucleotides (SNPs) identified in the core genome, a dendrogram of the relations of the studied strains was constructed.Results and discussion. All 16 Y. pestis strains from the Ustyurt, Mangyshlak, Kopetdag, and Karakum desert foci belong to the 2.MED1 branch of the medieval biovar. All investigated strains from the first three foci and most of the strains from the Karakum focus are in the Caspian 2.MED1 branch, and three strains from the Karakum desert focus are included in the Central Asian one. We have revealed several waves of dissemination of the strains under the 2.MED1 phylogenetic branch of Y. pestis of the medieval biovar in the Eastern Caspian Sea region in the 20th century.

The aim of the work was to conduct phylogenetic analysis of Y. pestis strains, biovar altaica ssp. central asiatica, isolated in Gorno-Altai high-mountain and Sailyugem natural plague foci on the territory of Russia and Mongolia in 1965–2020, by full-genome sequencing data.Materials and methods. To determine the population structure of the biovar altaica ssp. central asiatica, 34 whole genome sequences were used (including 20 Y. pestis strains of the biovar altaica, 18 of which were sequenced by us). To isolate DNA from the Y. pestis strains, a PureLink Genomic DNA Mini Kit (Invitrogen, USA) was applied. Sequencing of the nucleotide sequences of Y. pestis strains was carried out in Ion PGM system Lifetechnologies. The analysis and processing of the obtained data were performed with the help of Newblergs Assembler 2.6 and IonTorrent Suite software package, 3.4.2. The search for SNPs was performed using the Wombac 2.0 program. The Maximum Likelihood dendrogram was built in the PhyML 3.1. The dendrogram was visualized using the FigTree 1.4.3 software.Results and discussion. Based on the data of whole genome analysis, taking into account the 1871 revealed polymorphic nucleotides, the spatial structure of the biovar altaica ssp. central asiatica has been determined. It includes several phylogeographic branches: the Kurai-Tarkhatinskaya (cluster 0.PE4a-1) and the Ulandryk-Mongolian (0.PE4a-2), which is in agreement with the geographical regions of the isolation of strains forming these branches in the Altai Mountains. The Kurai-Tarkhatinskaya branch is further divided into the Kurai (sub-cluster 0.PE4a-1-1, formed by the strains of 2009–2018) and Tarkhatinskaya (subcluster 0.PE4a-1-2, formed by the strains of 2012–2020) sub-branches, while the Ulandryk-Mongolian branch of evolution is split into sub-branches represented by strains from the Ulandryk meso focus (sub-cluster 0.PE4a-2-2, strains 1965–2010) and the Sailyugem focus of Mongolia (sub-cluster 0.PE4a-2-1, strains 1964–1990).

The aim of the research was to assess epizootic activity of natural plague foci in the Russian Federation in 2021 and provide a prognosis for 2022. Activation of epizootic process has been detected in Central-Caucasian high-mountain natural plague focus after a recess since 2007. Local epizootics persist to develop in Tuva Mountain and Gorno-Altai highmountain plague foci. Total area of epizooties in Russia in 2021 amounted to 1649.5 km2. 28 plague microbe strains were isolated. Animals infected with plague were not found in Tersko-Sunzhensky low-mountain, Dagestan plain-piedmont, Precaspian north-western steppe, Volga-Ural steppe, Trans-Baikal steppe, Volga-Ural sandy, Caspian sandy and EastCaucasian high-mountain natural plague foci. It is demonstrated that epidemiological welfare as regards plague in Russia in 2017–2021 was achieved through annual epizootic monitoring of plague-enzootic territories, timely epizooty detection and preventive activities aimed at reducing the risk of infection. Substantiated has been the forecast for tense epidemiological situation on the territory of Karachay-Cherkessia, Kabardino-Balkaria, Altai Republic and Tuva Republic in 2022. A new Epitracker application has been proven to be prospective for rapid assessment of actual epidemiological situation in natural plague foci.

The aim of the study was to develop a test system that allows for detecting plague pathogen DNA in clinical and biological samples, environmental objects with the simultaneous determination of its appurtenance to the main and non-main subspecies, differentiation of the altai biovar central asiatica subspecies separately. Materials and methods. Primer sets for specific genetic markers have been selected using the VectorNTI 10 software, optimal conditions for PCR were determined for RotorGene devices. To assess the specificity and sensitivity of the developed set of reagents, 44 strains of microorganisms were used, of which 19 were Yersinia pestis strains and 25 strains of heterologous microorganisms. The diagnostic sensitivity of “GenPest-subspecies/Altai-RGF” is 98.6 % with a confidence level of probability of 91 %. The diagnostic specificity of “GenPest-subspecies/Altai-RGF” is ≥ 99 % with a confidence level of 91 %. Results and discussion. A medical product “A set of reagents for the detection and differentiation of plague pathogen strains of the main and non-main subspecies (altai biovar, subspecies central asiatica exclusively) by the polymerase chain reaction with hybridization-fluorescent registration of results in real-time mode (GenPest-subspecies/Altai-RGF)” has been developed. The set of reagents passed the state registration in accordance with the established procedure. The use of the developed set of reagents is relevant for the Gorno-Altai high-mountain plague focus of the Russian Federation and the adjacent part of Mongolia.

For many years, arbovirus infections have been a global health problem and one of the urgent threats to the sanitary and epidemiological well-being of the population. Climatic conditions, species diversity and abundance of vectors, epidemiological and demographic factors are of fundamental importance for the emergence and persistence of natural foci of arbovirus infections. In the Socialist Republic of Vietnam (SRV) and other countries of the Asia-Pacific region, the most complex epidemiological situation is observed in regard to a number of arboviral infectious diseases transmitted by mosquitoes, inter alia to dengue fever. In this review we analyzed the literature data to identify the features of the circulation of some arboviruses in Vietnam, such as dengue virus, Zika, Chikungunya, Japanese encephalitis virus, Dabie virus, and the routes of their transmission and spread. It is shown that the climatic, ecological, epidemiological and demographic conditions existing on the territory of Vietnam contribute to the spread of pathogens of many arboviruses. Areas of more active circulation and ways of spreading pathogens of arbovirus infections have been identified. Based on the data obtained, it is necessary to conduct annual epidemiological and epizootiological survey of the territory of the SRV in order to identify markers of pathogens and determine the boundaries of natural foci of arbovirus infectious diseases which will enhance and increase the effectiveness of preventive and anti-epidemic measures.

Community-acquired pneumonia is a polyetiological infectious disease of bacterial or viral nature. In most cases, it is caused by pathogens such as Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Staphylococcus aureus, Legionella spp. However, despite that a wide range of modern diagnostic methods have been introduced into laboratory practice, the etiology of the disease can be determined only in 40–60% of cases. Here, we analyzed the causative agents of community-acquired pneumonia and relevant markers samples of clinical material collected from patients undergoing treatment in the medical facilities of the city of Saratov and the Saratov Region during the period from July to August, 2020, coupled to increase number of cases of new coronavirus infection COVID-19. Clinical material (oropharyngeal swabs, saliva, sputum, blood and blood serum) was obtained from 129 patients and investigated by using microbiological, immunoserological and molecular genetic methods. For this, there were used transport and nutrient media, diagnostic drugs, reagents, discs with antibacterial domestic and foreign drugs registered in the Russian Federation. As a result, 82 (63.6%) patients were found to have markers of the pathogen COVID-19 (viral RNA or specific antibodies of IgM and/or IgG classes), whereas 42% of cases had overlapped RT-PCR and ELISA data. There was a predominance of severe clinical forms of the disease in the group of patients with pneumonia caused by SARS-CoV-2 virus (17.1%), compared with pneumonia of another etiology (12.8%). No marked differences in specific pattern of the accompanying microflora and its sensitivity to antibacterial agents were observed in persons with/without markers of COVID-19. While being examined by bacteriological methods, S. aureus, K. pneumoniae, S. pneumoniae, M. pneumoniae, Acinetobacter spp., both in monoculture and in associations, were isolated from samples of clinical material collected from the majority of patients. In 49.6% of cases, pathogenic microflora, including pathogens causing community-acquired pneumonia, has not been identified, which may be due to the use of antibacterial drugs before the collection of clinical material and treatment applied due to comorbid chronic diseases.

Introduction. Acute febrile diseases kill more than 250,000 people annually in West Africa. Malaria and typhoid fever traditionally occupy most of the total structure of registered fevers. However, these data do not fully reflect the true overall disease patterns in the West African region. This is due to the fact that diagnosis is mainly based on the clinical signs of the infectious process, suggesting that a certain number of diseases may be caused by arboviruses. The detection of specific antibodies (ABs) to infectious pathogens in the blood sera of residents of a particular area is a reliable indicator of the circulation of these pathogens in a particular territory. The aim of this study was to determine the prevalence of antibodies to a number of arboviruses: Dengue (DENV), West Nile (WNV) (family Flaviviridae), Crimean-Congo hemorrhagic fever (orthonairo)virus (CCHFV), Batai (Batai virus), Bhanja (BHAV) (order Bunyavirales), Chikungunya (CHIKV), and Sindbis (SINV) (family Togaviridae) in the population of the Republic of Guinea. Material and methods. In total, a panel of 2,620 blood serum samples from people living in all landscape and geographical areas of Guinea was collected for the study. Detection of IgG antibodies was performed using an enzyme-linked immunoassay (ELISA). Results. In total, ABs to Batai virus were detected in 144 samples (5.5%), BHAV in 58 (2.2%), WNV in 892 (34.0 %), DENV in 659 (25.2 %), CCHFV in 58 (2.2 %), CHIKV in 339 (12.9 %), and SINV in 52 samples (2.0 %). Discussion. The obtained results indicate serological evidence of the spectrum of arboviruses in the population of all landscape and geographical zones of the Republic of Guinea, confirming their active circulation in this territory. Conclusion. Given the high epidemiological significance of arbovirus infectious diseases, it is an urgent task to continue studying its share in the structure of febrile diseases in the territory of the Republic of Guinea.

The aim of the work was the identification and genetic characterization of Vibrio cholerae O1 strains of the El Tor biovar sensitive to polymyxin B among isolates imported to Russia.Materials and methods. We used 56 toxigenic and non-toxigenic strains of V. cholerae isolated from patients and from the environmental samples on the territory of Russia in 1970-2020. Resistance to polymyxin B was determined according to MR4.2.2218-07. The ability of strains to form a biofilm on the abiotic surface was assessed by a photometric method. Nucleotide sequences of genes were determined using UGENE 1.32 and MEGA X software. Phylogenetic analysis and tree construction were performed using "maximum parsimony" method in MEGA X software.Results and discussion. Two genetically modified strains of V. cholerae O1 biovar El Tor, M1509 and 3265/80, which were imported to Russia from India in 2012 and 2014, respectively, were identified. The analysis of 12 genes responsible for the resistance of V. cholerae O1 biovar El Tor strains to polymyxin B demonstrated that these strains contain the allele of the carRS gene, which is typical for all strains of cholera vibrio sensitive to polymyxin B. Study of V. cholerae M1509 and 3265/80 phylogeny based on SNP analysis showed that they fall into the same cluster with isolates containing the carRS allele isolated in India (2015) and Bangladesh (2018). V. cholerae M1509 and 3256/8 strains had the ability to form a biofilm similar to those observed in other genetically modified strains of cholera vibrio included into analysis.Conclusion. Highly virulent strains of the cholera agent with altered diagnostically significant features are imported into Russia, which should be taken into account when identifying V. cholerae O1 biovar El Tor strains isolated from patients and environmental samples during monitoring studies.

Objective of the study was to perform a comparative analysis of molecular-genetic properties in non-toxigenic Vibrio cholerae O1 strains biovar El Tor, isolated in the Republic of Kalmykia and on cholera endemic territories and to reveal their phylogenetic relations to toxigenic isolates.Materials and methods. We have carried out bio-information analysis of whole genome sequences of 60 cholera vibrio strains from endemic as regards cholera regions and from Kalmykia. The presence of pathogenicity and endemicity islands in their genomes has been determined. Specifed have been the sequence-types of the examined strains and whole genome SNP-analysis conducted.Results and discussion. Non-toxigenic El Tor vibrios circulating in Kalmykia are clustered into two major genotypes: ctxA–tcpA+VPI-2+VSP– and ctxA–tcpA–VPI-2Δ+VSP–, where VPI-2 Δ+ signifes the presence of deletions of varying length in the genome of this pathogenicity island. Only the latter one is found in regions endemic for cholera. In addition, ctxA– tcpA+VPI-2+VSP+ populations circulate in cholera endemic foci, not found in Kalmykia. 17 sequence-types were identifed among the studied strains (by seven housekeeping gene loci). Phylogenetic analysis performed using SNP-typing demonstrated the absence of close genetic relation between the ctxA–tcpA+VPI-2+VSP– vibrios from Kalmykia and both toxigenic and non-toxigenic vibrios with different composition of pathogenicity and pandemicity islands in the genome. At the same time, genetic proximity of ctxA–tcpA–VPI-2Δ+VSP– cholera vibrios from endemic cholera foci with those isolated in Kalmykia was detected, which may indicate the possibility of their recurrent importation into the territory of Russia. Non-toxigenic V. cholerae strains found in the territory of Kalmykia are characterized by a high genetic diversity. Circulation of the strains with unique sequence-types suggests their potential for long-term persistence on this territory. At the same time, phylogenetic closeness and identity of certain strains with strains from endemic territories can be an evidence of repeated importation.

The aim of the study was a comprehensive analysis of the phenotypic and genetic properties of Yersinia pestis strains isolated in the Sarydzhaz and Upper-Naryn high-mountain foci of the Tien Shan in 2019–2020; determination of the present-day population structure and areal of these highly virulent strains of the plague pathogen.Materials and methods. Studies of biochemical properties (fermentation of carbohydrates, nutritional requirements), virulence (in vitro and in laboratory animals), molecular-genetic analysis and whole genome sequencing of Y. pestis strains isolated in the Sarydzhaz and Upper-Naryn high-mountain foci in 2019–2020 have been carried out. We used Y. pestis strains from the foci of the Tien Shan and Pamir-Alai dated 1928–2016 for the comparison. Whole genome sequencing was performed using the Ion S5 XL System. Phylogenetic analysis was performed on the basis of 1443 identified core SNPs in 36 Y. pestis strains of various phylogenetic lines included in the analysis. The construction of dendrograms was carried out using the Maximum Likelihood algorithm, PHYML program, HKY85 model.Results and discussion. It is established that all Y. pestis strains isolated in the Sarydzhaz and Upper-Naryn high-mountain foci in 2019–2020 belong to the 0.ANT5 phylogenetic branch of the ancient biovar of the main subspecies. Genome-wide sequencing revealed the presence of two 0.ANT5 clones, the first of which consists of strains from the basin of the river Kooylu in the Sarydzhaz focus, dated 2020. The second powerful clone includes the strains of 2012–2020 isolated in the Sarydzhaz and Upper-Naryn foci. The high virulence of the isolated strains has been shown. It was concluded that further study of the territories of the highmountain foci of the Tien Shan and Pamir-Alai is necessary to establish the current boundaries of the 0.ANT5 areal, as well as to identify the circulation areas of Y. pestis of other phylogenetic lineages.

The aim of the review was to consider the principles and criteria for the formation of funds of service microbiological collections and the specialized State collection of pathogenic bacteria (SCPB) at the RusRAPI “Microbe”. The rapid pace of characterization, study, and use of microbial diversity makes the development of criteria for the selection of microorganisms for permanent storage in collections particularly relevant. The number and format of these criteria are determined by the tasks the collection centers of different levels and specialization are facing. Service collections form their funds by depositing or acquiring type, reference, educational strains. In recent years, the practicability of expanding the range of strains, the deposition of which is desirable in service collections, has been recognized. These are strains characterized by phylogenetic, genomic, metabolic, ecological uniqueness; with a fully sequenced genome; known and emerging plant, animal and human pathogens that caused disease outbreaks; used in international research projects; having biotechnological and economic significance. The main task of the SCPB as a specialized state collection of pathogenic bacteria of groups I–II is to preserve strains characterizing the intraspecific diversity and populations of pathogens circulating in natural foci or in certain territories of the Russian Federation, isolated during epizootics, local or epidemic outbreaks. The selection criteria for strains for permanent storage are their ecological, phenotypic, and genetic peculiarities. The preservation of such a collection is important for future research using new technologies and tracking the evolution of pathogenic bacteria – causative agents of particularly dangerous infectious diseases.

The aim of the study was to characterize and carry out molecular-genetic identification of Yersinia pseudotuberculosis strains isolated in the Sarydzhaz high-mountain focus of the Tien-Shan.Materials and methods. The Y. pestis and Y. pseudotuberculosis cultures were differentiated according to their sensitivity to diagnostic bacteriophages, motility, urea fermentation, and pesticin production. Whole genome sequencing was performed using the Ion S5 XL System (Thermo Fischer Scientific). Ion Torrent Suite software package, 5.12 and Newbler gsAssembler 2.6 were used for data processing and de novo assembly of raw read sequences. The dendrogram was constructed using the Maximum Likelihood method applying the PhyML 3.1 software.Results and discussion. Strains of Y. pseudotuberculosis were isolated from museum mixed with Y. pestis cultures obtained from marmots in the Sarydzhaz high-mountain focus. According to whole genome SNP analysis, they belong to the phylogenetic group O:3 serovar, which is widespread throughout the world. Y. pseudotuberculosis is often present in mixed with Y. pestis cultures, isolated from rodents, which should be taken into account when carrying out laboratory diagnostics of plague in natural foci.

Emergence of various genovariants of the SARS-CoV-2 virus, which are characterized by a higher ability to spread and a more severe clinical manifestations compared to the initial variants, require molecular-genetic monitoring of strains circulating in the Russian Federation.The aim of the work was to identify the VOC SARS-CoV-2 genovariants in the territory of the Republics of Bashkortostan, Tatarstan, Udmurtia, and Samara, Penza, Saratov, Ulyanovsk, and Orenburg Regions.Materials and methods. The identification of genovariants and the determination of the type of mutations was carried out by the Sanger fragment sequencing method.Results and discussion. The study examined 298 samples of clinical material obtained from the Centers for Hygiene and Epidemiology in the Republics of Bashkortostan, Tatarstan, Udmurtia, Samara, Penza, Saratov, Ulyanovsk, and Orenburg Regions. In 17 % of cases, the variability of the SARS-CoV-2 virus was observed for one or more markers: in three samples, a new coronavirus of the B. 1.1.7 line (“British”) was detected; in a number of cases, only one mutation was detected in the virus found in samples – deletion Y144 or substitution D138Y, E484K, N501Y, and very rarely two mutations – deletion Y144 and substitution E484K. The presence of the L141-G142-V143 deletion localized in the recurrent deletion region RDR2 of the S-gene was shown in 10 % of the cases. The data obtained indicate the heterogeneity in macroorganism of the population of the new coronavirus with the deletion L141-G142-V143, which leads to a change in the antigenic structure of the virus, which probably allows the virus to evade the immune response.

The aim of the work was to substantiate the forecast of the epidemiological and epizootiological situation in natural foci of plague in the Russian Federation, countries of the near and far abroad for the year of 2021. Characteristics of the distribution of Yersinia pestis strains of the main subspecies (subspecies pestis) of medieval and antique biovars, Caucasian (ssp. caucasica) and central Asian (ssp. central asiatica) subspecies by 45 natural foci of the CIS countries are presented in the paper. The persistence of a multidirectional trend in the dynamics of epizootic activity of natural foci of the CIS countries with the circulation of Y. pestis pestis strains of the medieval biovar of the 2.MED1 phylogenetic branch and the antique biovar of the 0.ANT5, 4.ANT phylogenetic branches in the current decade has been outlined. For the Russian Federation, the development of epizootics is predicted in the Gorno-Altai highland and Tuva mountain natural foci caused by the circulation of Y. pestis pestis strains of the antique biovar 4.ANT and Y. pestis of the Altai biovar of the Central Asian subspecies 0.PE4a in 2021. For the Republic of Kazakhstan, there is a high probability of preserving epizootic activity in the North Aral, Aral-Karakum, Balkhash, Mojynkum, Taukum desert and Ili intermountain natural foci with the circulation of Y. pestis pestis strains of the medieval biovar of the phylogenetic branch 2.MED1. For the Kyrgyz Republic, the forecast for the development of plague epizootics caused by Y. pestis pestis strains of the antique biovar 0.ANT5 phylogenetic branch in the Sarydzhaz and Upper Naryn high-mountain natural foci has been substantiated. A high epidemic risk of epizootic manifestations caused by highly virulent strains of Y. pestis pestis of antique biovars 0.ANT5, 4.ANT and medieval biovar 2.MED1 for the entire territory of the CIS countries is noted. The relevance of implementing forecasts of the epidemiological situation into practice, taking into account the molecular-genetic and epidemiological characteristics of Y. pestis strains circulating in areas of expected epizootic manifestations of plague, is highlighted.

The aim of the study was to develop and assess the efficacy of a method for Lujo virus RNA detection in clinical and biological samples using one-step real-time RT-PCR.Materials and methods. In order to select the conservative regions of the genome, we utilized the available in GenBank database Lujo virus sequences (https://www.ncbi. nlm.nih.gov/genbank) aligned in BioEdit 7.2.5 software package ( (IbisBiosciences, USA). To conduct one-round RTPCR, reverse transcriptase and TaqF-polimerase were used. Recombinant Escherichia coli strain, XL1-Blue, containing pGEM-T plasmid with inserted synthetically-generated fragment of the virus genome, was produced to make positive control sample (PCS). Constructed recombinant plasmids were used for creating RNA-containing PCS with protective protein shell of MS2-phage. Determination of specificity of the developed method was performed with the help of control panel of RNA and DNA of 23 viral strains related to 10 families; the sensitivity – the panel of biological samples artificially contaminated with PCS. Further testing was carried out at the premises of laboratory of the Russian-Guinean Center for Epidemiology and Prevention of Infectious Diseases (Kindia, Republic of Guinea) on 265 blood sera from practically healthy persons, 110 blood sera of cattle, 83 suspensions of ticks, and 165 suspensions of organs of small mammals collected in the territory of Guinea.Results and discussion. Two conservative polymerase gene fragments have been chosen as targets for Lujo virus RNA detection using RT-PCR. The combination of primers and probes has been experimentally selected, optimum composition of reaction mixture for PCR and mode of RT-PCR set-up established, as well as control samples C+, internal control, positive control sample developed. Sensitivity of the proposed method is 5·103 GE /ml, specificity – 100 %.

The novel coronavirus (SARS-CoV-2) pandemic, dubbed COVID-19, has become one of the most serious challenges for human populations in the vast majority of countries worldwide. Rapid spreading and increased mortality related to it required new approaches to manage epidemic processes on a global scale. One of such approaches was based on analyzing SARS-CoV-2 seroprevalence associated with COVID-19. Our aim was to summarize the results on assessing seroprevalence to the SARS-CoV-2 nucleocapsid antigen (Nc) in residents from 26 regions of the Russian Federation, carried out during the first wave of the COVID-19 epidemic.Materials and methods. Seroprevalence distribution was examined in 26 model regions of the Russian Federation according to the unified method developed by the Rospotrebnadzor with the participation of the Federal State Institution Saint Petersburg Pasteur Research Institute of Epidemiology and Microbiology. Such approach implied formation of a group of volunteer subjects in model geographic region who were tested by ELISA for anti-Nc serum antibody level in peripheral blood. Analyzed primary data obtained in separate regions were either accepted for publication or released.Results. The current paper finalizes the data obtained in all 26 regions of the Russian Federation. The total SARS-CoV-2 seroprevalence was 19.5 (10.0–25.6)% with the maximum and minimum value found in the Kaliningrad Region and the Republic of Crimea, respectively (50.2% vs. 4.3%). A pattern of age-related seroprevalence distribution indicates insignificant predominance of seroprevalence among subjects of 1–17 years old: 22.1 (13.1–31.8)%. Among COVID-19 convalescents positive for SARS-CoV Nc antibodies it reached 60.0 (40.0–73.3)%. The number of contact persons comprised 6285 subjects or 8.5% of total volunteer cohort, with the level of seroprevalence reaching up to 25.3 (17.95–35.8)%. A direct correlation was revealed between levels of seroprevalence in convalescent and contact volunteers. In addition, the reproductive number for SARS-CoV was calculated comprising 5.8 (4.3–8.5) suggesting that one convalescent subject can infect at least 4 healthy individuals. A high level of asymptomatic forms of COVID-19 among seropositive subjects was confirmed empirically comprising up to 93.6 (87.1–94.9)%.Conclusion. A single cross-sectional study performed during 2020 June–August timeframe allowed to assess pattern of sex- and agerelated COVID-19 seroprevalence for general population in 26 Russian Federation regions. The data obtained may serve as a basis for the longitudinal cohort investigation with serial subject sampling. The timing and duration of study will be determined by dynamics of ongoing COVID-19 epidemic.

The global community is experiencing one of the largest infectious disease outbreaks in the 21st century. In the Saratov Region, the first case of new coronavirus infection was confirmed on March 19, 2020.The maximum increase in cases was noted between May 15 and June 30, during that time the total number of infected people in the region increased from 1526 to 6444. Since July 2020, a stable incidence level of new coronavirus infection has been observed in the Saratov Region, without a steady decline.The aim of the study was to assess the status of population immunity to the SARS-CoV-2 virus among residents of Saratov and the Saratov Region under the COVID-19 epidemic.Materials and methods. In the period from June 23 to July 26, 2020, a serological study of blood samples from 3372 volunteers of different age groups was conducted. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of reagents “ELISA anti-SARS-CoV-2 IgG” produced by the State Scientific Center of Applied Microbiology and Biotechnology of the Rospotrebnadzor (Russia).Results and discussion. In general, the incidence of COVID-19 in the Saratov Region is taking place against the background of moderate seroprevalence to the SARS-CoV-2 virus, accompanied by a high incidence of non-apparent (asymptomatic) forms of the infectious process. The absence of clinical symptoms of the disease, in the context of the limited use of methods for determining the RNA of the SARS-CoV-2 virus in PCR (11 % of the region’s population) makes it difficult to assess the real spread of the virus in the population and to establish the timing of the formation of persistent herd immunity. A low rate of antibody response among individuals with a positive result of PCR analysis, as well as among volunteers who had an infection in May, June 2020, indicates a weak formation of the immune response, or the prevalence of individuals reacting mainly by activating the cellular link of the immune system in the population. The obtained results, although they need to be explained in a number of respects, can be applied to the organization of preventive measures, including vaccination, in the region.

The aim of the study was molecular-genetic identification and analysis of the phylogenetic relationship of Yersinia pestis strains isolated on the Ukok Plateau in 2020, in order to establish the current boundaries of the natural mega focus of plague in the Altai Mountains in Russia and Mongolia.Materials and methods. 37 strains of Y. pestis of the main subspecies isolated in the Tuva mountain and Gorno-Altai high-mountain plague foci and adjacent territories of Mongolia in 1971–2020 were studied. The whole genome sequencing of the strains was performed using the Ion S5 XL System (Thermo Fischer Scientific). Ion Torrent Suite software package 5.12 and Newbler gsAssembler 2.6 were used to process the data and assemble de novo the sequences of raw reads. The average size of the collected genome was 4.55 million base pairs. Core SNPs were detected by aligning the contigs of Y. pestis strains on the CO92 genome using the Snippy 4.6 program, then 28 SNP homoplasies were removed. The resulting set of SNPs contained only the core region of the genome (955 SNPs). The dendrogram was constructed using the Maximum Likelihood method applying the PhyML 3.1 program.Results and discussion. The current population structure of Y. pestis of the main subspecies, antique biovar, phylogenetic line 4.ANT, endemic to the foci of the Altai Mountains in Russia and Mongolia has been determined. The presence of 4.ANT-21 clone, which became widespread in the territory of these natural foci of plague at the begining of the XXI century, was revealed. It is shown that three strains isolated on the Ukok Plateau in 2020 belong to clone 4.ANT-21. According to phylogenetic analysis, evidence of 4.ANT circulation on the Ukok Plateau before 2018 was obtained. The lesson that has been learned is that it is necessary to study the territories of Mongolia, Kazakhstan and China bordering the Ukok Plateau in order to establish the current boundaries of the 4.ANT mega focus.

The review presents the materials on the use of mobile laboratories, developed in the Russian Federation, in the framework of four main areas: monitoring of territories to identify the circulation of pathogens of natural-focal infectious diseases; monitoring of territories during the exacerbation of the epizootic situation; participation in the elimination of outbreaks of infectious diseases; monitoring of territories to control and predict the epidemiological and epizootiologic situation in preparation for mass events. The tactical and technical characteristics and the procedure for organizing the operation of the mobile laboratory for monitoring and diagnostics mounted on the platform of the KamAZ chassis are considered. A distinctive feature of the laboratory from the existing Russian and foreign counterparts is the availability of the necessary conditions for conducting research using bacteriological analysis, rapid and accelerated diagnostic methods, and performing a full cycle of works – from the preparatory stage to the destruction of infected material. Hightech equipment allows the realization of two research schemes: the first – bacteriological analysis alongside the PCR, which ensures high reliability of the results; the second – conducting the PCR at the first stage, and when identifying genetic markers of the pathogen – performing bacteriological analysis of positive samples in order to isolate the culture of the pathogen and identify it subsequently. The second scheme will reduce the volume of bacteriological studies; make changes in the tactics of epizootiological survey. Tests of the mobile laboratory have demonstrated the effectiveness of its use in the epizootiological examination of natural plague foci, including cross-border ones. Owing to the use of a mobile laboratory in the Gorno-Altaisk high-mountain natural focus of plague, a new epizootic site was identified, located in a remote area, used by the population as a summer pasture for grazing domestic animals. The use of mobile laboratories will strengthen the laboratory base of institutions that monitor particularly dangerous, natural-focal and other dangerous infectious diseases; will help to bring the advanced diagnostic technologies directly to the natural focus, reduce the risk of epidemic complications due to plague and other particularly dangerous infections in cross-border natural foci.

Objective of the study was to analyze phylogenetic relation of the strains and dissemination routes of Yersinia pestis in Kara Kum desert focus in XX century.Materials and methods. We have carried out whole genome sequencing of 8 Yersinia pestis strains isolated in Kara Kum desert focus between 1949 and 1985. We also used nucleotide sequences of 16 Y. pestis strains from neighboring foci of East and North Caspian Sea region dated 1917–2002, sequenced at the premises of RusRAPI “Microbe” on Genestudio Ion S5XL platform (Thermo Fischer Scientific). Phylogenetic analysis was performed based on 1720 identified core SNPs. Phylogenetic dendrogram was constructed using Maximum Likelihood algorithm, PhyML v. 3.1 software package, and nucleotide substitution model GTR.Results and discussion. On the basis of whole-genome SNP analysis of Y. pestis strains from Kara Kum desert focus, West and North Caspian Sea region foci analysis of plague agent populations circulating in Turkmenistan in XX century was conducted. It has been demonstrated that three separate waves of Y. pestis dissemination swept the territory of Kara Kum desert focus. The origin of the first one, registered in 1912, plague outbreak in south-eastern part of the focus and its etiological agent remain unspecified so far. The second wave is associated with distribution of North-Aral 2.MED1 population of medieval biovar in 1949–1970, which led to the emergence of epizootic activity in 1949, as well as subsequent cases and outbreaks of plague in this territory in the middle of the XX century. In the mid-second half of the past century, one more 2. MED1 dissemination wave from the North Balkhash region hit the Kara Kum desert focus. This central-asian population has also taken root in the natural biocoenosis of the Kara Kum focus. The data obtained testify to active processes of distribution of Y. pestis of medieval biovar in East Caspian Sea region in southern sub-zone of Eurasian deserts in XX century.

Objective: to study the evolution of SARS-CoV-2 virus in the process of adapting to human organism duringthe current pandemic.Materials and methods. Database (GISAID) on nucleotide sequences of SARS-CoV-2 virus genome, obtained from clinical samples during the period of late December, 2019–July, 2020. Phylogenetic tree diagram construction was carried out applying BioNumerics v.7.6 software using Maximum parsimony algorithm.Results and discussion. The most substantial change in the genomes of SARS-CoV-2 virus are associated one-time mutations in ORF1b (P314L) and S (D614G) genes, as a result of which the overwhelming majority of identified isolates of this virus have the stated pair of substitutions to date. Many researches link the substitution in S (D614G) gene to the decreased pathogenicity in the strains that contain it, which may be also explained by enhanced methodology of patient treatment in the course of pandemic. The effect of the mutation in ORF1b (P314L) gene has not yet been investigated. P314L and D614G mutations are closely related and only their combined presence in the genome favored the dissemination of the genovariants of SARS-CoV-2 virus. Analysis of congregated epidemiological data testifies to the fact that the spread of new genovariants may be associated with biological properties facilitating human-to-human transmission. Thereat, associated decrease in lethality may reflect not only advancements in methods of treatment, but possible attenuation of virulent properties. Thus, observed growth in dissemination potential against the background of decrease in virulence is, probably, one of the forms of adaptation of new coronavirus to human population and, apparently, will remain in the future as the integration of SARS-CoV-2 virus into the structure of seasonal ARVI agents.

Objective of the study was to conduct whole-genome sequencing of the vaccine strain Francisella tularensis 15 NIIEG and determine, based on the results, its phylogenetic relationships and the genetic organization features.Materials and methods. Whole-genome sequencing of F. tularensis 15 NIIEG strain was performed on Ion PGM (Ion Torrent, USA) and MinIon (Oxford Nanopore Technologies, UK) platforms. Alignment of readings obtained to the whole-genome of F. tularensis subsp. holarctica LVS (CP009694, USA, 2015) was performed using the software package DNASTAR Lasergene 15.3. Hybrid assembly of reads into contigs was performed by means of Unicycler v. 0.4.4, using data obtained by semiconductor sequencing technology (Ion PGM) and nanopore sequencing (MinIon). Phylogenetic analysis was performed on the basis of single nucleotide polymorphism (SNPs) data located in the core part of F. tularensis genome. Maximum parsimony algorithm was used to construct a dendrogram using the obtained data of common SNP-matrix.Results and discussion. The close relations of F. tularensis 15 NIIEG strain with F. tularensis LVS vaccine strain used in the countries of Western Europe and North America was confirmed. Searching for common single mutations characteristic of F. tularensis 15 vaccine strains of NIIEG and LVS, permitted to find 5 unique SNPs that distinguish them from all other 228 F. tularensis strains used in the comparison. Comparative genomic analysis ofF. tularensis 15 NIIEG vaccine strain and virulent strains revealed in its structure two extensive 526 bp deletions (genes pilA and pilE) and 1480 bp (genes encoding lipoprotein). Similar deletions are also present in the genome of the F. tularensis LVS vaccine strain.

Objective of the study was to identify epidemiological peculiarities of HFRS outbreak in the territory of the Saratov Region in 2019 and to determine the key factors contributing to the intensity of epidemic process.Materials and methods. Analyzed are the data on 2702 cases of HFRS registered in the territory of the Saratov Region in 2019, obtained from the Rospotrebnadzor Administration in the Saratov Region and Center of Hygiene and Epidemiology in the Saratov Region. The basic method of investigation was epidemiological one with application of advanced information technologies.Results and discussion. Retrospective analysis of epidemic HFRS manifestations in the Saratov Region showed that HFRS outbreak of 2019 was the largest over the period of disease reporting, both by the number of cases (2702) and by the duration. Early onset of increase in the incidence (may) and allocation of the majority of cases to the territory of the natural park “Kumysnaya Polyana”(75 %) should be considered as characteristic features of the outbreak. We have conducted epidemiological zoning of the Saratov Region allowing for dividing the Region into four types of territories which differ by the level of risk of HFRS exposure (very high, high, medium, and low), as well as distinguishing the most hazardous in terms of HFRS infection territories of Saratov. The key factors affecting the surge in HFRS cases were high numbers of infected rodents during spring months of 2019 due to mild and extremely snowy winter of 2018–2019; reduction in forest engineering works aimed at turning the focal territory into aesthetic forestry. The change in the character of exploitation of 9 % of the natural park “Kumysnaya Polyana” resulted in the increase of population contacts with natural-focal complexes. Mass visits to natural focus during early spring period against the background of low alertness to risks of HFRS infection led to explosive growth of HFRS incidence.