Isabella V. Savina

The aim of the work was to analyze the epidemiological situation on cholera in the world and in Russia and to make its forecast for 2026. Proactive epidemiological surveillance data showed that over the period of 2016–2025 there was an upward trend in cholera incidence worldwide: 5,474,013 cases were documented in 91 countries. The proportion of patients was distributed among countries as follows: Yemen (53.4 %), Afghanistan (11.7 %), Democratic Republic of the Congo (6.3 %), Nigeria (4.7 %), Somalia (3.2 %), South Sudan (2.5 %), Sudan (2.5 %), and Haiti (2.4 %). In 2025, 42 countries reported 589,571 cases and 8,140 deaths (5.1 % more than in 2024). The increase in cholera cases in 2025, compared to 2024, amounted to 5.12 %. Population migration remained the main risk-forming factor for the spread of cholera to different countries. In the Russian Federation, monitoring of labor migration was introduced with the organization of medical observation of arriving persons for seven days after arrival from cholera affected countries. As a result of monitoring surface water bodies in 2025, 50 non-toxigenic strains of Vibrio cholerae O1 circulating in the territory of the Russian Federation and belonging to different genetic lines were isolated. A decrease in the number of acute intestinal infections was noted from 13 (2024) to 5 (2025), caused by non-toxigenic V. cholerae nonO1/nonO139. Forecast for 2026: the risk of cholera importation persists due to the expected increase in the intensity of labor migration. Registration of acute intestinal infections and extra-intestinal infections caused by non-toxigenic strains of V. cholerae nonO1/nonO139 is probable. Detection of non-toxigenic strains of V. cholerae O1 and their clonal complexes circulating in water bodies will continue. Stable epidemiological situation on cholera in the Russian Federation is predicted for 2026.

The aim of the study was to analyze the data from monitoring cholera prevention measures as part of epidemiological surveillance in the constituent entities of the Russian Federation. Materials and Methods . An epidemiological and statistical analysis of the data provided by territorial bodies of the Rospotrebnadzor using developed forms was conducted through the departmental information system report.gsen.ru on a weekly basis from April to October in 2023 and 2024. Results and discussion . In light of the risk of importation and spread of cholera during the period of 2022–2024, and in accordance with the directives of the Rospotrebnadzor, enhanced monitoring for cholera was implemented across the territory of the Russian Federation. Additional sampling points were introduced at temporary accommodation centers, from wastewater before treatment, from transboundary rivers and other water objects, in cities with population over one million, in port cities, at resorts of the Azov and Black Seas, at wastewater discharge sites from infectious disease hospitals (or departments), and in areas where organized groups of labor migrants live and work. The timing of scheduled monitoring studies was changed in certain territories. The training of specialists was strengthened. The paper presents selected indicators of specialist training, the results of testing for cholera for individuals with symptoms of acute intestinal infections, and the results of monitoring studies on cholera in the territory of the Russian Federation in 2023 and 2024, including the detection of cholera vibrios O1 and non-agglutinating (NAG) vibrios depending on the nature of water use at sampling points, which indicate the presence of conditions for the possible spread of the cholera pathogen by water route in the event of infection importation in 75 % of the country’s entities.

The aim of the work was to analyze the monitoring data on contamination of water bodies with Vibrio cholerae О1 during epidemiological surveillance of cholera in Russia. Materials and methods. The analysis of the data on the isolation of cholera vibrios O1 from water bodies (2015–2024) was carried out using official statistical reports from the Rospotrebnadzor Administrations in the constituent entities of the Russian Federation and anti-plague institutions. Studies of biological properties of the strains were performed in accordance with MR 4.2.3745-22; genome-wide sequencing was conducted on the MiSeg platform (Illumna, USA). Results and discussion. Information about 848 strains of V. cholerae O1, including V. cholerae O1 ctx А ⁺ tcpA ⁺ (3), V. cholerae O1 ctxA ^– tcpA ⁺ (48) and V. cholerae O1 ctxA ^– tcpA ^– (797) in 30 entities of the Russian Federation has been investigated. V. cholerae O1 El Tor ctxA ^– tcp А ^– and V. cholerae O1 El Tor ctxA ^– tcpA ⁺ were isolated from 72 water bodies: 46 rivers, 13 ponds, 8 lakes, and other objects in various climatic regions, mainly in the Atlantic-continental European (forest) part, as well as in the continental East Siberian and monsoon Far Eastern areas. The data on contamination of water bodies with V. cholerae O1 in the administrative territories of the Russian Federation, varying by types of epidemic manifestations of cholera, federal districts; sampling points; on the results of epidemiological investigations using genome-wide sequencing of V. cholerae O1 ctxA ^– tcp А ^– strains are provided in the paper.

Objective : to analyze epizootic and epidemic manifestations of naturally occurring focal infections (tularemia, ixodes tick-borne borelliosis, West Nile fever, Crimean hemorrhagic fever, Q-fever, leptospirosis, yersiniosis, hemorrhagic fever with renal syndrome) in the Rostov region in 2024. Materials and methods : the studies were conducted in accordance with current regulatory documents. The objects of the study were small mammals, birds, blood-sucking arthropods, environmental objects, and donor blood serum. Studies to find antigens of infectious disease pathogens were conducted using solid-phase ELISA and PCR. Results : The nosological profile of natural focal infections has been determined, which includes six main nosological units: West Nile fever; Ixodes tick-borne borreliosis, Q-fever, Crimean hemorrhagic fever, leptospirosis and tularemia. In a crosssectional seromonitoring study, 754 residual blood serum samples from a conditionally healthy population were tested for the pathogens of the studied infections. As a result of comprehensive epizootological studies, a modern range of small mammals has been established, consisting of 12 species of rodents and insectivores. Conclusion : The analysis of the epidemiological situation in 2024 confirmed the presence of natural foci of dangerous infectious diseases in the Rostov region.

147 human tularemia cases were registered on the territory of the Russian Federation (the relative incidence rate per 100,000 population is 0.1) in 20 regions of the country in 2024. An unfavorable epidemic situation persists in the territories of the Republic of Karelia (50 tularemia cases); an increase in the incidence was recorded in the KhantyMansi Autonomous District – Yugra (58) and in the Sverdlovsk Region (12), which accounts for 81.6 % of all cases of tularemia in the country. 31 cultures of Francisella tularensis were identified in six regions of the Russian Federation. In 2024, 937,962 people were vaccinated and revaccinated against tularemia. In 2025, the high risk of epidemic complications of tularemia will remain in the Central Federal District (Ryazan, Orel and Bryansk Regions), the Southern Federal District (Volgograd, Rostov Regions and the Republic of Crimea), the North Caucasusian Federal District (Stavropol Region), the North-Western Federal District (Arkhangelsk Region, Republic of Karelia, Nenets Autonomous District), Ural Federal District (Sverdlovsk Region and Khanty-Mansiysk Autonomy, District Yugra), Siberian Federal District (Novosibirsk and Tomsk Regions, The Republic of Altai and Altai Territory), as well as in the Donetsk and Lugansk People’s Republics, Zaporozhe and Kherson Regions.

In 2024, during routine monitoring of surface water bodies in Sochi for cholera, non-toxigenic cholera vibrios of serogroup O1 were isolated. The aim of the work was to analyze the results of the epidemiological monitoring and characterize the molecular-genetic properties of the isolated strains. Materials and methods. The work uses the data obtained as a result of an epidemiological investigation of the causes of river contamination with cholera vibrios in Sochi. Whole-genome sequencing of isolated strains was performed on the MiSeq platform (Illumina). Genetic determinants of cholera vibrio pathogenicity were identified using the BioEdit and BLASTN software. Results and discussion. It was established that the probable cause of contamination of the Matsesta river waters was the entry of non-toxigenic cholera vibrios from patients with a mild course of the disease, with an erased form of the disease or vibriocarriers. The introduction of cholera vibrios into the Agura and Mzymta rivers could have occurred due to associated groundwater, since a karst aquifer lies in the waters of all three rivers. Bioinformatics analysis showed that the isolated cultures of cholera vibrios in the waters of the Matsesta, Agura and Mzymta rivers are genetically identical, constitute a single clonal complex with strains isolated from surface water bodies of the Russian Federation, and are not imported from abroad. Vibrio cholerae O1 strains isolated from environmental objects in 2024 and cultures isolated from patients with acute intestinal infection (AII) in the Kherson Region (2024) and Krasnodar Territory (2004) belonged to the same cluster. The results indicate the presence of optimal environmental conditions for the existence of cholera vibrios in the surface water bodies of Sochi, which necessitates extensive monitoring to its maximum, provided for type I territories for epidemic manifestations of cholera, with prompt molecular-genetic study of the isolated cultures.

The aim of the work was to analyze the peculiarities of the cholera epidemiological situation in the world and in Russia in 2024; forecast for 2025. The results of proactive epidemiological surveillance showed a continued upward trend in cholera morbidity in the world despite of the decrease in this indicator in 2024 (762 830 cases in 42 countries) as compared to 2023 (816 235 in 47 countries). A special feature was the import of a polyantibiotic-resistant Vibrio cholerae O1 El Tor strain from Tanzania to Island Mayotte. Active labor migration to the Russian Federation (RF) from countries with unfavorable cholera situation was noted (11 686 foreigners, 88.17 % – from India). No cholera patients (vibrio carriers) were identified in RF. The features of epidemiological situation have been established: two toxigenic V. cholerae O1 strains similar to the one isolated in 2023, and one toxigenic strain of NAG, documented in RF for the first time, were detected in surface water bodies. It has been determined that the non-toxigenic V. cholerae O1 strain, which caused a case of acute intestinal infection, and waterborne O1 strains circulating in Russia belong to the same clone. For the first time, the non-toxigenic V. cholerae O139 strain was isolated from a patient with acute intestinal infection. An increase in the number of non-toxigenic O1 strains isolated from water bodies was noted (335 in 2024, 52 in 2023), mainly due to the clonal complex (250 strains, Krasnodar Territory) spread through karst waters. Diseases caused by non-toxigenic NAG vibrios V. parahaemolyticus and V. fluvialis, were detected. The forecast for 2025 covers the risks of cholera importation, including cases caused by antibiotic-resistant strains; increase in labor migration from countries with an unfavorable cholera situation; the likelihood of detecting toxigenic O1 and nonO1/nonO139 strains in the environment, an increase in the number of acute intestinal infections caused by non-toxigenic cholera and other pathogenic vibrios; possible detection of extra-intestinal infections, an increase in the number of non-toxigenic V. cholerae O1 in environmental objects. It is advisable to start monitoring studies earlier (April) and finish them later (October) in RF in 2025 in type I territories classed according to epidemic manifestations of cholera.

Objective: retrospective analysis of the results of monitoring studies of environmental water bodies in Rostov-on-Don for the presence of V. cholerae for the period from 1989 to 2023 at stationary sampling points assigned to the Rostov-on-Don Anti-Plague Institute of Rospotrebnadzor, identification of trends and features of the dynamics of isolation and biological properties isolated strains. Materials and methods: in the period from 1989 to 2023, 4362 samples from aquatic ecosystems were examined. The organization and conduct of research was carried out in accordance with regulatory and methodological documents (SanPiN 3.3686-21, MUK 4.2.3745- 22, MUK 4.2.3746-22). Sequencing of isolated strains was performed on the MiSeq (Illumina) platform. Results: during the analyzed period, V. cholerae strains were found in all studied reservoirs of the Rostov-on-Don: in the Don, Temernik and Dead Donets rivers, mainly in July and August. Of the 122 isolated strains, 8 are epidemiologically significant (toxigenic strains) and 114 are nontoxigenic. The largest number of strains was isolated in 2022 — 21 strains. V. cholerae strains O1 (119 strains) and O139 (3) of serogroups, biovar classic and El Tor (Ogawa, Inaba and Gikoshima serovars) were found. Conclusions: epidemiological risks of the introduction of the cholerae pathogen from endemic countries, as well as from neighboring countries, in cases of complications of the epidemic of this infection, remain. In the surface reservoirs of the Rostov-on-Don, there are favorable conditions for the circulation of V. cholerae and the risk of spreading infection by water, in case of contamination by the cholerae pathogen of aquatic ecosystems.

Background:The risks of cholera importation into Russia are determined by the intensity of the epidemic process in endemic countries of Southeast Asia, the Eastern Mediterranean, and Africa. The assessment of risk factors for cholera importation and spread forms the basis of the risk-oriented methodology in proactive epidemiological surveillance, which ensures timely forecasting of the epidemiological situation, preparedness, and rapid response in case of its deterioration, as well as the prevention of severe consequences. Aim:To assess the effectiveness of proactive epidemiological surveillance of cholera in Russia in 2023–2024. Materials and methods:a risk-oriented approach was employed, based on the systematic collection of official data on global cholera incidence from sources such as the Weekly Epidemiological Record (WHO), official and regional WHO websites, internet resources including ProMED-mail post, ECDC, and other platforms. The study adhered to regulatory documents issued by the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing for 2023–2024 and utilized operational epidemiological analysis data from the Reference Center for Cholera Monitoring in Russia. Whole-genome sequencing (WGS) and genome assembly were conducted on the MiSeq (Illumina) platform, and genetic determinants were identified in WGS data using BioEdit 7.2.5 and BLASTN 2.2.29. Statistical data processing was performed using the StatSoft STATISTICA 6.1.478 Russian software. Results:A comprehensive analysis of global cholera incidence data was conducted, providing a realistic forecast of the risks of cholera importation into Russia in 2023. The epidemic preparedness of Rospotrebnadzor and the Ministry of Health of Russia was assessed, followed by a prompt response to two imported cholera cases detected in Tambov region and Moscow in 2023, both originating from India. Timely identification of these cases, including genomic and phylogenetic characterization of the pathogens, was achieved. Infection foci were localized and eliminated, preventing further spread. Cholera monitoring in Russia continued throughout 2024, with preventive measures implemented to minimize the risks of cholera importation and spread. Conclusions:The analysis of the 2023–2024 monitoring results demonstrated the effectiveness of the proactive epidemiological surveillance system, which relies on early identification of cholera importation risks and their precursors, forecasting, rapid response to potential complications in epidemiological situation, and control of objects and factors contributing to infection spread. The epidemiological stability regarding cholera in Russia was ensured.

The paper presents an analysis and assessment of risks of complication of epidemiological situation regarding cholera in the Russian Federation and a forecast for 2024. It briefly characterizes the dynamics of the epidemic process around the world during the last decade (2013–2022). The forecast of cholera importation into the Russian Federation, due to activity of the epidemic process in endemic countries, has been confirmed. In 2023, two cases of cholera importation from India were reported. It was established that the toxigenic strains isolated from patients belonged to the currently dominant in the world “post-Haitian” group, including in India and Bangladesh, with the genotype ctxB7 tcpA^CIRS rtxA4a VSP-IIΔ0495-0512. Furthermore, non-toxigenic Vibrio cholerae O1 strains were isolated from samples of biological material from persons arriving from India, containing preCTX prophage and distinct from the strain (ctxAB^– tcpA^EТ–) isolated from a patient with acute intestinal infection (Zaporozhye Region, Melitopol). Nontoxigenic NAG vibrios were isolated from 13 patients with acute intestinal infections, which is 1.9 times more than in 2022. Regardless of importations, a strain of V. cholerae O1 (ctxB1⁺tcpA^EТ) of the “pre-Haitian” group was isolated from a water sample of a surface reservoir. 52 non-toxigenic V. сholerae O1 strains were found on the territory of 11 constituent entities of the Russian Federation, which is 18.9 % more than in 2022. In 2024, epidemiological risks of cholera importation from endemic countries to any administrative territory of the Russian Federation remain. The risks of epidemic manifestations of cholera are especially high in the territories of the constituent entities of the Russian Federation which are under ongoing emergency, due to migration processes, and the impact of other risk-forming factors that contribute to an increase in the degree of contact of the population with water bodies contaminated with cholera vibrios. If epidemic foci of cholera are to emerge in a neighboring country, there will be a high probability of spread of this infection in the stated constituent entities of the Russian Federation and in other territories of southern Russia. In the absence of epidemic manifestations of cholera, the possibility of occasional detection of toxigenic O1 serogroup strains in water samples due to unidentified introductions from cholera-affected areas cannot be ruled out.