Epidemic Process Research Articles

MEASLES MORBIDITY IN THE NORTHWESTERN FEDERAL DISTRICT OF THE RUSSIAN FEDERATION

Abstract Introduction. The COVID-19 pandemic profoundly affected measles epidemic process. On the territory of the Russian Federation, restrictive measures contributed to the continuation of measles circulation, but the pandemic created the prerequisites for further development of outbreaks. We have to analyze measles morbidity in the Northwestern Federal District in the pre- and post-Covid period. Material and methods. Blood serum samples (n=3179) collected from patients with maculopapular rash and fever were studied using ELISA. Results. In the Russian Federation in the years 2008 – 2010 measles incidence remained at extremely low level due to the importation of measles virus of different genotypes from global regions. In the territories of the Northwestern Federal District, during the period preceding the COVID-19 pandemic, measles incidence was characterized as sporadic. A major measles outbreak occurred in 2018-2019, with the disease being recorded in 6 of the 11 territories of the Northwestern Federal District. Since the introduction of quarantine measures, the number of verified measles cases has dropped sharply. The last case of measles in the region was reported in May 2020. In 2021, measles was not recorded in the territories of the Northwestern Federal District. The rise in measles incidence began at the late 2022 due to imported measles from Tajikistan. In 2023, measles incidence in the district amounted to 2.5 per 100,000 population. Measles continued to spread in 2024. In 2023 and 2024, the disease occurred mainly in unvaccinated subjects or those with unknown vaccination history; mostly children. The spread of measles in the territories of the Northwestern Federal District in 2022 and early 2023 was facilitated by late diagnosis and isolation of the first measles patients; introduction of measles into population groups not vaccinated against measles; delays in the supply of vaccines for populational immunization, including in outbreak areas. In general, measles circulation has resumed in the territories of the Northwestern Federal District.

Mass vaccination of shift workers at a large construction site as a measure to prevent socially significant infections

Relevance. Biological emergencies caused by infectious agents are characterized by acute onset, rapid spread, and involvement of large populations in the epidemic process. Epidemics develop especially quickly in large, densely populated areas sharing the same living, eating, and working conditions, which is typical of shift workers involved in major construction sites. Vaccination remains the most effective method to prevent socially significant infectious diseases and avoid epidemic outbreaks.The objective is to analyze the experience of mass vaccination organization and management among shift workers at a large construction to prevent socially significant infectious diseases.Methods. The focus of the study is immunoprophylaxis of socially significant infections at a large construction site in the Far Eastern region of Russia; the study subjects are shift workers residing in the Russian Federation, neighboring, or far–fetched countries. For the study period from January 2020 through December 2024, the daily average number of on–site workers was (27,182 ± 2,625) (ranging from 12,508 to 39,120 depending on the phase of work). During their on–site stay, workers were accommodated in temporary camps equipped with dormitories made from modular buildings; meals was served in camp canteens, and transportation to and from the work locations was provided by company buses. Vaccines represented domestic formulations used for immunoprophylaxis of the following socially significant infections: influenza (“Ultrix Quadri”, “Sovigripp”, “Grippol Plus”), pneumococcal infection (“Prevenar–13”), coronavirus infection (vector vaccines “Sputnik V”, “Sputnik Lite”), measles (live–attenuated) and tick–borne viral encephalitis (“EnceVir”, “Klesch–E–Vac”). All vaccines administered in accordance with the official guidelines. The effectiveness of vaccination organization and management was assessed using logical analysis, expert evaluation, and epidemiological research. Statistical data processing was carried out using generally accepted methods of statistical analysis.Results and discussion. The retrospective analysis of mass vaccination measures among shift workers of a large construction site against socially significant infections were obtained. Vaccination of shift workers was carried out in a designated vaccination room, a temporary vaccination station of the on–site infectious disease hospital, as well as in mobile vaccination stations deployed in temporary shift camps accommodating construction workers. The paper elaborates the layout of vaccination infrastructure, logistics, and information on the total number of preventive vaccinations performed at the site in 2020–2024. In fall 2020, before Covid–19 vaccines were available, mass influenza vaccination was administered, covering 80.7 % of the total number of workers staying at the construction site, thus allowing to prevent an outbreak of influenza and acute respiratory viral infections amid the ongoing epidemic of a new coronavirus infection. Thereafter, influenza vaccination was conducted annually, covering at least 60–65 % of the total number of project employees. Vaccination against pneumococcal infection was conducted jointly with influenza vaccination, primarily in managers, engineers, and technical staff, as well as in high–risk individuals. These efforts prevented the development of severe invasive pneumococcal infection and significantly reduced the incidence of non–invasive clinical cases. The estimated data on the cost–effectiveness of influenza and pneumococcal vaccination was confirmed by decreased incidence of influenza, acute respiratory viral infections, and pneumonia. Mass vaccination against COVID–19 was carried out in 2021 and 2022, eventually allowing to completely stabilize the epidemiological situation at the site and minimize the incidence of a new coronavirus infection. Due to the emerging threat of imported measles, a large–scale (more than 16,000 shift workers) preventive vaccination against measles was conducted in winter–spring 2020. In 2023–2024, measles vaccination was conducted mainly for epidemic indications. The annual vaccination against tick–borne viral encephalitis allowed to eliminate clinical cases of the disease among project employees, despite a significant number of tick bites, including virus–positive cases. Overall, over 130,000 immunizations against socially significant infections were administered during 2020–2024.Conclusion. Mass vaccination of shift workers against most critical socially significant infections allowed to prevent epidemic outbreaks of infectious diseases and enabled timely and prompt progress of a large–scale construction project.

Epidemic models with digital and manual contact tracing

Abstract We analyse a Markovian SIR epidemic model where individuals either recover naturally or are diagnosed, leading to isolation and potential contact tracing. Our focus is on digital contact tracing via a tracing app, considering both its standalone use and its combination with manual tracing. We prove that as the population size n grows large, the epidemic process converges to a limiting process, which, unlike with typical epidemic models, is not a branching process due to dependencies created by contact tracing. However, by grouping to-be-traced individuals into macro-individuals, we derive a multi-type branching process interpretation, allowing computation of the reproduction number R. This is then converted to an individual reproduction number $R^\mathrm{(ind)}$ , which, in contrast to R, decays monotonically with the fraction of app-users, while both share the same threshold at 1. Finally, we compare digital (only) contact tracing and manual (only) contact tracing, proving that the critical fraction of app-users, $\pi_{\mathrm{c}}$ , required for $R=1$ is higher than the critical fraction manually contact-traced, $p_{\mathrm{c}}$ , for manual tracing.

Hepatitis B Virus Genotypes and Subgenotypes Circulating in Belarus

Approximately 800–900 new cases of chronic forms of hepatitis B are reported in Belarus annually. Compulsory vaccination, introduced to the country in the mid-90s, produces a certain positive effect on reducing the number of HBV cases. However, around 75,000 patients with chronic hepatitis B are estimated to live in the country at the moment. The main goal of this research was to determine the genotypes/subgenotypes of the hepatitis B virus and establish their role in maintaining the epidemic process in the country. Serological (CMIA, ELISA), molecular biological (PCR, sequencing), and bioinformatic (phylogenetic analysis) methods have been used to obtain results. As studies have shown, in 722 (81.7%) samples, genotype D has been determined; in 156 (17.7%), genotype A; in 3 (0.3%), genotype C; and only in 1 sample (0.1%), genotype B. In two cases (0.2%), a recombinant form of the hepatitis B virus has been detected. The epidemic process of hepatitis B in the country is supported mainly by the circulation of “local” variants of the virus. At the same time, there are occasional introductions of new genetic variants from outside of the country.

Работа поликлиники в условиях подъема острых респираторных вирусных заболеваний и роль главной медицинской сестры в обеспечении противоэпидемических мероприятий

Abstract The relevance of the problem is due to the high virulence and pathogenicity of the coronavirus infection COVID-19 caused by the SARS-CoV-2 virus. The objective of the study was to evaluate the effectiveness of the complex of medical-organizational and anti-epidemic measures developed and implemented in the city out-patient clinic in the context of the COVID-19 pandemic, as well as the seasonal increase in the incidence of acute respiratory viral infections and influenza. Material and methods. The object of the study was the epidemic process and a set of medical, organizational and anti-epidemic measures among the assigned population in a typical city out-patient clinic associated with the coronavirus pandemic. The source of information was publications in domestic scientific journals on the stated topic, data obtained from the official website of the Office of the Federal State Statistics Service for Khabarovsk Krai, Magadan Oblast, Jewish Autonomous Region and Chukotka Autonomous Okrug, as well as collections of statistical data published by the Medical Information and Analytical Center of the Ministry of Health of Khabarovsk Krai for 2020–2022. Results and discussion. The article presents an analysis of the work of the Khabarovsk City Out-patient Clinic in the context of the pandemic of a new coronavirus infection. The study focuses on an integrated approach to combating the spread of the SARS-CoV-2 virus, as well as the prevention of a seasonal rise in acute respiratory viral infections and influenza. The author describes in detail the development and implementation of comprehensive anti-epidemic measures, assesses their impact on creating a safe environment within the medical institution. Conclusions. To ensure the safety of patients and employees when providing medical care, a well-established chain of preventive and anti-epidemic measures in a medical institution is of particular importance. Compliance with all preventive measures, a comprehensive approach to these measures reduce the risks of the spread of acute respiratory viral infections, influenza, COVID-19.

Efficient and accurate simulation of infectious diseases on adaptive networks

Mathematical modelling of infectious disease spreading on temporal networks has recently gained popularity in complex systems science to understand the intricate interplay between social dynamics and epidemic processes. As analytic solutions can usually not be obtained, one has to resort to exact stochastic simulation algorithms, yet these have remained infeasible for the large sizes of realistic systems. Here, we introduce a rejection-based stochastic sampling algorithm with high acceptance probability (‘high-acceptance sampling’; HAS), tailored to simulate disease spreading on adaptive networks. We prove that HAS is exact and can be multiple orders faster than Gillespie’s algorithm. While its computational efficacy is dependent on model parameterization, we show that HAS is applicable regardless on whether contact dynamics are faster, on the same time-scale, or slower than the concurrent disease spreading dynamics. The algorithm is particularly suitable for processes where the spreading- and contact processes are co-dependent (adaptive networks), or when assumptions regarding time-scale separation become violated as the process unfolds. To highlight potential applications, we study the impact of diagnosis- and incidence-driven behavioural changes on virtual Mpox- and COVID-like epidemic and examine the impact of adaptive behaviour on the spreading processes.

Gender and age ratio in patients hospitalized and deceased from COVID-19. Vestsi Natsyyanal’nai akademii navuk Belarusi

The COVID-19 pandemic determines the relevance of conducting a study of the gender and age structure in hospitalized and deceased patients.The purpose of the study is to identify the patterns of the COVID-19 epidemic process in connection with the gender and age characteristics of hospitalized adults and to identify the gender and age groups wich most susceptible to hospitalization and mortality from COVID-19.An analysis of the structure of hospitalized and deceased from COVID-19 by gender and age was carried out. Data from statistical registration forms of adults hospitalized in one of the city clinical hospitals in Moscow in 2020–2021 were used. Data processing was carried out using a set of standard statistical methods. To identify risk groups for hospitalization and mortality, statistical correction of the population composition by gender and age was used.Data on risk groups for hospitalization and mortality among the population of Moscow at the early stage of the COVID-19 pandemic were obtained. It has been established that the risk group for hospitalization with COVID-19 is young men (average age 39.0 ± 5.0 years). They are 1.5 times more likely to be hospitalized with COVID-19 than younger women. According to COVID-19 mortality rate, the risk group is middle-aged (53.1 ± 4.3 years) and elderly (68.3 ± 4.5 years) men, for whom the mortality risk is higher than in women of the same age (3.3 and 2.2 times, respectively). Also at risk for mortality are men of age of 75–90 years, the mortality rate among them was 57 %.The results of the study allow to identify true risk groups for hospitalization and mortality due to COVID-19, complement new knowledge into the patterns of epidemiological analysis, which is an important component of epidemiological surveillance for making management decisions to the spread prevention of SARS-CoV-2 spread prevention and planning for the provision of medical care for identified gender and age risk groups.

Carleman approximants for non-linear differential systems

Abstract We examine a method introduced by Torsten Carleman a century ago to approximate the solution of non-linear differential systems. His idea consists in replacing the non-linear system with an infinite-dimensional linear one. Carleman approximants are obtained when solving a truncated version. We describe the linearization process and present two different approaches to apply the Carleman technique. In the first one, which is the common case, the Carleman approximants are centred at an equilibrium point in phase space. The resulting linear system is always homogeneous, and higher orders of approximation are usually analytically solvable. The closer the point of interest is to the equilibrium point, the more accurate the approximate solution. In a way, this approach may be viewed as an extension of the so-called local, or qualitative, analysis of non-linear differential systems. In the second one, the approximants are built up around the initial condition. In this novel approach, there is a gain in accuracy at the price of solving a non-homogeneous linear system that allows for an analytical solution too. We found a noteworthy pattern in the analyticity properties of the approximants that explains this improved behaviour. The connection with the Koopman operator and related methods is commented on. A number of systems are worked out intended to provide evidence of the practical utility of the Carleman approach. We also derive approximate solutions for the Susceptible-Infected-Removed epidemiological model, which leads to an extended classification of the evolutionary stage of an epidemic process.

Impact of official and civil information correlation on information-epidemic coupling dynamics in multiplex network

Abstract Official and civil information, as distinct information sources, significantly influence public behavior and the dynamics of epidemic transmission. In this paper, we propose a three-layer U1A1U1-U2A2U2 -SIS coupled model to analyze the co-evolution process of official information dissemination, civil information dissemination and epidemic transmission, considering the interdependencies between the information dissemination channels. The first layer describes the official information dissemination process. The second layer models the civil information dissemination process, considering the effects of perceived risk costs and the role of the correlation between official and civil information. The third layer represents the epidemic transmission process, highlighting the impact of the correlation between official and civil information on epidemic transmission. Then, using the microscopic Markov chain approach, we describe the information-epidemic coupled dynamics and derive the epidemic outbreak threshold. Our research demonstrates that a stronger positive correlation between official and civil information raises the epidemic threshold and suppresses the scale of epidemic transmission. Furthermore, individuals' adoption of civil information should involve a more thorough assessment of the infection risk based on their personal circumstances, which can contribute to more effective epidemic control. Moreover, enhancing infected individuals' accurate comprehension of official information can effectively curb the transmission of the epidemic. Our study highlights the importance of both official and civil information dissemination in epidemic management and provides insights for policymakers in developing effective public health and communication strategies.

Smart epidemic control: A hybrid model blending ODEs and agent-based simulations for optimal, real-world intervention planning.

Optimal intervention planning is a critical part of epidemiological control, which is difficult to attain in real life situations. Ordinary differential equation (ODE) models can be used to optimize control but the results can not be easily translated to interventions in highly complex real life environments. Agent-based methods on the other hand allow detailed modeling of the environment but optimization is precluded by the large number of parameters. Our goal was to combine the advantages of both approaches, i.e., to allow control optimization in complex environments. The epidemic control objectives are expressed as a time-dependent reference for the number of infected people. To track this reference, a model predictive controller (MPC) is designed with a compartmental ODE prediction model to compute the optimal level of stringency of interventions, which are later translated to specific actions such as mobility restriction, quarantine policy, masking rules, school closure. The effects of interventions on the transmission rate of the pathogen, and hence their stringency, are computed using PanSim, an agent-based epidemic simulator that contains a detailed model of the environment. The realism and practical applicability of the method is demonstrated by the wide range of discrete level measures that can be taken into account. Moreover, the change between measures applied during consecutive planning intervals is also minimized. We found that such a combined intervention planning strategy is able to efficiently control a COVID-19-like epidemic process, in terms of incidence, virulence, and infectiousness with surprisingly sparse (e.g. 21 day) intervention regimes. At the same time, the approach proved to be robust even in scenarios with significant model uncertainties, such as unknown transmission rate, uncertain time and probability constants. The high performance of the computation allows a large number of test cases to be run. The proposed computational framework can be reused for epidemic management of unexpected pandemic events and can be customized to the needs of any country.

Is the Existing Measles Vaccination Schedule in the Russian Federation Effective?

Relevance. During the period of long–term measles vaccination in Russia, the age of those who were vaccinated with live measles vaccine changed several times – from 9 to 15-18 months, until scientific research proved the optimal age of 12 months. During the period of measles elimination, when population immunity is formed mainly through immunization, and the artificial active immunity of mothers protects children of the first year of life for a shorter period of time than natural active immunity, the incidence of this infection in children under 1 year of age is of particular importance for managing the epidemic process of measles. The aim of this study is to assess the importance of measles in the epidemic process of children under the age of 1 year during the elimination of infection, the effectiveness of the current measles vaccination regimen.Materials and methods. The measles incidence in children under 1 year of age was analyzed in absolute and relative terms for the period from 2010 to 2024. For more u For a more in-depth analysis, the years of the increase in the incidence of 2012, 2014, 2019, 2023 and 2024 were selected, when the patterns of involvement of this analyzed group in the epidemic process of measles were most pronounced. The Pearson coefficient was used to determine the correlation.Results and discussions. The configuration of the measles incidence curve in children in the first year of life completely coincides with the dynamics of measles incidence in the general population, and a strong positive correlation (r=+0.99) confirmed the dependence of the incidence of the analyzed age group on the overall incidence. Further in-depth analysis showed that children under the age of 1 are not the leading group at high risk of infection, but rather passively participate in the epidemic process, becoming involved in the process with an increasing number of sources of infection. Thus, the proportion of sick children during the years of the rise in morbidity ranged from 7.77% to 15.87%, but even in the year of the maximum increase in the overall incidence, the but at the same time, even in the year of the maximum increase in the overall incidence recorded in 2024, when the total number of cases exceeded 22 thousand people, the analyzed indicator did not exceed 9.69%. Children aged 6-11 months were more likely to get sick, accounting for an average of 75.98%, while the proportion of children with measles in the first five months averaged 24.02%. The structure of measles cases was dominated by unvaccinated individuals. During the years of the rise in the incidence of 2012, 2014, 2019, 2023, 2024, the proportion of the unvaccinated accounted for respectively 77,0%, 75,2%, 84,4%, 88,8%, 89,5%. Among them, children of the first year of life accounted for a small percentage – only 20,6%, 14,9%, 9,4%, 8,7% and 10.7%.Conclusion. The results of the analysis of the incidence of children under one year of age confirmed the validity of vaccination tactics at 12 months and at 6 years of age in our country. The incidence of measles in children under the age of vaccination directly depends on the vaccination against measles in their immediate environment, therefore it is very important to maintain population immunity at a level of at least 95.0%. At the moment, there is no reason to change the scheme, which does not exclude its change in the event of new vaccines or changes in the epidemic situation for measles.

Critical dynamics of epidemic processes with Lévy-like diffusion

Critical dynamics of epidemic processes with Lévy-like diffusion

Characteristics of the epidemic process of measles, rubella and mumps and assessment of their seroprevalence at the present stage

Introduction. The problem of vaccine-preventable infections requires assessing the state of herd immunity through serological monitoring. The aim. To study the epidemiological features of measles, rubella and mumps and to estimate their seroprevalence in the last decade in Moscow. Materials and methods. Forms of federal statistical observation; State reports «On the state of sanitary and epidemiological well-being of the Moscow population»; official EMISS data for 2012–2023 were used to conduct a retrospective analysis of incidence. Blood serum samples (n = 7458) from healthy individuals stratified by age were tested for the presence of IgG antobodies to measles, rubella and mumps using the ELISA. Statistical data processing was performed using Microsoft Excel and SPSS Statistics v.27 (IBM). Results. The analysis of epidemiological situation in Moscow in 2012–2023 revealed the presence of multidirectional trends: wave-like increase in the incidence of measles, stabilization of rubella cases registration and unstable incidence of mumps with an upward trend. A high prevalence of IgG antibodies to rubella virus was determined, preventing the spread of infection among the population. The formed level of herd immunity to mumps does not allow reducing the incidence to sporadic cases. The observed trend of increasing measles incidence can be explained by the accumulation of non-immune individuals among the population. Conclusion. The significant proportion of seronegative individuals indicate the necessity to adjust vaccination prevention tactics and implement measures for mopping-up and catch-up immunization of the population against measles and mumps, especially in risk age groups.

Small-coupling dynamic cavity: A Bayesian mean-field framework for epidemic inference

A novel generalized mean-field approximation, called the small-coupling dynamic cavity (SCDC) method, for epidemic inference and risk assessment is presented. The method is developed within a fully Bayesian framework and accounts for noncausal effects generated by the presence of observations. It is based on a graphical model representation of the epidemic stochastic process and utilizes dynamic cavity equations to derive a set of self-consistent equations for probability marginals defined on the edges of the contact graph. By performing a small-coupling expansion, a pair of time-dependent cavity messages is obtained, which capture the probability of individual infection and the conditioning power of observations. In its efficient formulation, the computational cost per iteration of the SCDC algorithm is linear in the duration of the epidemic dynamics. While the method is derived for the susceptible-infected (SI) model, it is straightforwardly applicable to many other Markovian epidemic processes, including recurrent ones. This linear complexity is particularly advantageous for recurrent epidemic processes, where inference methods are typically exponentially complex in the duration of the epidemic dynamics. The method exhibits high accuracy in assessing individual risk, as demonstrated by tests on the SI model applied to various classes of synthetic contact networks, where it performs on par with belief propagation techniques and generally exceeds the performance of individual-based mean-field methods. Additionally, the method was applied to recurrent epidemic models, where it showed interesting performance even for relatively large values of the infection probability, highlighting its versatility and effectiveness in challenging scenarios. Although convergence issues may arise due to long-range correlations in contact graphs, the estimated marginal probabilities remain sufficiently accurate for reliable risk estimation. Future work includes extending the method to non-Markovian recurrent epidemic models and investigating the role of second-order terms in the small-coupling expansion of the observation-reweighted dynamic cavity equations. Published by the American Physical Society 2025

A unifying class of compound Poisson integer‐valued ARMA and GARCH models

Abstract INAR (integer‐valued autoregressive) and INGARCH (integer‐valued GARCH) models are among the most commonly employed approaches for count time series modeling, but have been studied in largely distinct strands of literature. In this paper, a new class of generalized integer‐valued ARMA (GINARMA) models is introduced which unifies a large number of compound Poisson INAR and INGARCH processes. Its stochastic properties, including stationarity and geometric ergodicity, are studied. Particular attention is given to a generalization of the INAR() model which parallels the extension of the INARCH() to the INGARCH(, ) model. For inference, we consider maximum likelihood, Gaussian quasi‐likelihood, and moment‐based approaches, along with likelihood ratio tests to distinguish between selected instances of our class. Models from the proposed class have a natural interpretation as stochastic epidemic processes, which throughout the article is used to illustrate our arguments. In a case study, different instances, including both established and newly introduced models, are applied to weekly case numbers of measles and mumps in Bavaria, Germany.

CURRENT FEATURES OF THE HEPATITIS EPIDEMIC PROCESS IN THE VINNYTSIA REGION

Aim. The aim of this study is to assess the epidemiological situation regarding the incidence of hepatitis A virus (HAV) in the Vinnytsia region from 1964 to 2024, and to formulate recommendations for improving the system of preventive and anti-epidemic measures that may help reduce the incidence in the future. Materials and methods. The study is based on the analysis of statistical data on HAV incidence in the Vinnytsia region over 60 years. Epidemiological, sanitary-statistical, and serological methods were used to assess incidence and identify risk factors. Additionally, studies were conducted to detect serological markers in high-risk groups to evaluate immunity levels in the population. Data analysis involved comparing incidence trends over the years, considering socio-economic and migration factors. Results. It was found that sporadic outbreaks of hepatitis A in the Vinnytsia region are related to general socio-economic conditions, including income levels, infrastructure status, and adherence to sanitary norms. Furthermore, migration processes play an important role, as a significant proportion of cases are registered among individuals who have recently returned from regions with higher epidemic risks. Fluctuations in the incidence rate were observed in different years, with a notable increase in 2023, partly due to the worsening sanitary situation in the region, non-compliance with hygiene standards in public places, and increased internal migration. Conclusions. The study confirmed the need for improving epidemiological surveillance and monitoring, as well as implementing more effective preventive measures, such as expanding vaccination among vulnerable population groups. Special attention should be paid to children and individuals living in high-risk areas. The high level of serological prevalence among the adult population indicates a lack of immunity in most children, highlighting the need for enhanced vaccination to prevent potential epidemics in the future.

Climate Anomaly Sums as a Researching Tool for the Epidemic Process of West Nile Fever

Long-term dynamics of climate indicators is a significant factor determining the course of the West Nile fever epidemic process. Based on epidemiological monitoring data and climate modeling results, a search was made for new predictors of sporadic outbreaks that can expand the understanding of the logic of the spread of the fever pathogen using the example of a large endemic focus in the Volgograd region. Based on the ecological characteristics of the strain circulating in the region, a new approach to determining the time frame of the epidemic season is proposed, taking into account the optimal temperatures for the development of the virus. The relationship between positive and negative climate anomalies (air temperature, precipitation) and West Nile fever incidence was studied. The strongest correlations were demonstrated by polynomial cubic models, including the sums of negative precipitation anomalies and the sums of positive temperature anomalies. The study emphasizes the importance of shifting the epidemiological paradigm towards taking into account climate anomalies when assessing the risks of the spread of vector-borne infections.

The trend of the HIV infection epidemic during the COVID-19 pandemic in the Republic of Тajikistan

The aim. Analysis of the features of the development trend of the HIV epidemic process during the COVID-19 pandemic in the Republic of Tajikistan.Materials and methods. The data on the prevalence and incidence of HIV infection among the general population during the COVID-19 pandemic were retrospectively analyzed based on data from the Republican Center for the Prevention and Control of AIDS of the Ministry of Health and Social Protection of the Republic of Tajikistan.Results and discussion. An analysis of the epidemic process during the development of HIV infection in the Republic of Tajikistan shows that the country still has a high risk of infection both among the most vulnerable cohorts of people and among the general population. During the period 2018–2019 (before the development of the COVID-19 pandemic), the largest number of new cases of HIV infection among the general population was detected. The epidemic process, starting in 2018, has tended to gradually decrease the incidence and mortality rates of HIV infection among the general population. In 2018, 1,421 new cases of HIV infection were detected. By the end of 2023, this figure was 1,100 cases, that is, it decreased by 1.3 times. In 2020, 1,095 HIV cases were identified, which is 20.5% lower than in 2019 (n=1,320), i.e. before the pandemic. In addition, the coverage of the population with HIV testing was 805,120 people, which is 1.3 times less (n=1,062,509) in 2019. During the COVID-19 pandemic, the prevalence of coronavirus among HIV-infected people was 0.31% of the total number of this cohort of patients.Conclusion. The COVID-19 pandemic, despite a slight decrease in the incidence of HIV infection, did not have a significant impact on the development of the HIV epidemic in the country. This trend is, in particular, associated with a decrease in the volume of HIV testing and with restrictive measures introduced in the country due to the worsening epidemiological situation with COVID-19.

Epidemiological Situation on Leptospirosis in the Rostov Region in 2024

The aim of the study was to investigate the leptospirosis manifestation peculiarities in the Rostov Region with an assessment of the natural foci epizootic activity and the epidemic significance of infection. Materials and methods. In 2024, an epizootiological study of 15 administrative territories was conducted. Small mammals (314 specimens of 12 species) were captured in open stations. The material from the animals was studied using bacteriological, microscopic, serological and molecular-genetic methods. The testing of 577 blood sera of people from selected groups of conventionally healthy population living in the 18 administrative districts of Rostov Region and Rostov-on-Don city was conducted using ELISA with detection of IgG and IgM to leptospirosis causative agents. Results and discussion. Specific antibodies to leptospirosis pathogens in animals were found in 11.5 % of samples from nine species of small mammals: house mouse, pygmy wood mouse, field vole, yellow-necked mouse, mound-building mouse, lesser white-toothed shrew, pygmy shrew, social vole, brown rat. Leptospira spp. infecting serogroups have been identified: Sejroe, Icterohaemorrhagiae, Canicola, Grippotyphosa, Pomona, Tarassovi. PCR-positive result was obtained for a sample from a pygmy wood mouse. Seroepidemiological studies of the conventionally healthy population have revealed the presence of specific antibodies to Leptospira in their blood in 14 administrative territories. The total level of seropreva­lence was 12.7 %. The serogroup structure of the immune layer of the population in the Rostov Region is as follows: Grippotyphosa (28.5 %), Pomona (23.2 %), Canicola (21.4 %), Tarassovi (7.1 %), Sejroe (5.3 %). Positive reactions to several serogroups were noted in a number of serа. The conducted studies evidence the existance of active natural foci of leptospirosis on the territory of the Rostov Region and involvement of the population in the epidemic process.

On the Results of Serological Evaluation and a Necessity of Surveillance over West Nile Virus among Population in the Khabarovsk Territory

The aim of the study was to evaluate intensity of contacts of the Khabarovsk Territory population with West Nile virus (WNV) based on the results of serological screening during 2022–2023. Materials and methods. Clinical material (blood sera) of 233 residents of the Khabarovsk Territory was tested for the presence of specific antibodies to WNV. Information on retrospective manifestation of West Nile fever (WNF) between 2010 and 2023 was obtained from scientific literature and reports presented to the Rospotrebnadzor Administration in the Khabarovsk Territory by Reference Center for Monitoring the WNF Pathogen at the premises of the Volgograd Research Anti-Plague Institute of the Rospotrebnadzor. Results and discussion. Specific IgM to WNV were detected in 15 out of 233 surveyed people. Among them, 11 individuals were hospitalized in medical organizations of the Khabarovsk Territory with the diagnosis of “tick-borne rickettsiosis”, “Ixodidae tick-borne borreliosis”. Positive results for IgG antibodies were revealed in 38.2 % of the samples. With the exclusion of antigenic cross-reactions to the tick-borne encephalitis virus, the level of the immunity to the West Nile virus was 9.0 %. The results of antibody avidity index showed that 90.1 % of positive samples had IgG of low avidity (IA<50 %). The results of the research allow for assuming the presence of West Nile fever cases among the Khabarovsk Territory population. High frequency of detection of IgM (8.5 %) among patients of infectious hospitals may indicate active epidemic process. Identification of 90.1 % of low avidity IgG in samples that were positive for IgG-WNV also confirms recent contact (less than 3 months) with the agent of WNF.