Relevance. The study COVID-19 is due to its continued circulation in SARS-CoV-2 in the world and the beginning of an increase cases in Russia this season. 
Aims. To compare the trends of the COVID-19 epidemic process in terms of morbidity and mortality in epidemic and inter-epidemic periods among the Russian population. 
Materials and methods. The analysis of the incidence and mortality of COVID-19 in Russia, megacities and 54 cities was carried out according to the стопкоронавирус. рф and the computer database of the Influenza Research Institute. 
Results. In Russia, 9 epidemics of COVID-19 and 4 inter-epidemic periods have been egistered in 5 years, the first in the summer of 2022, then in 2023, 2024 and in 2025 (from January to May). There are similar trends in reducing morbidity and mortality in epidemics and inter–epidemic periods: at the same time, the dynamics of epidemics shows an increase in morbidity in the first 5 waves, and from the sixth – a decrease, and an increase in mortality with a peak in the fourth wave, and in the fifth – a decrease in mortality to a minimum in the ninth wave. In the dynamics of epidemics in St. Petersburg, 54 cities and the Russian Federation as a whole, the coefficients of the trend of increasing morbidity were lower (k=215, k=119.3, k=87.3) than the decrease in morbidity (k = -250, k = -134.8, k = -108.5). The coefficients of the trend lines of increased mortality from COVID-19 were greater (from k = 20 to k = 162) than the decrease (from k = -15.3 to k = -29), and in interepidemic periods, morbidity (from k=-5 to k=-10.5) and mortality (from k = -1.6 to k = -19.8). The first interepidemic period was shorter and higher in morbidity and mortality than the subsequent ones. The incidence rates, as well as the coefficients of the trend lines of increased incidence, were higher in the North-Western, Far Eastern, Siberian and Ural Federal Districts than in Central, Volga, Southern, and North Caucasian. During periods of epidemics, there was a tendency for the proportion of children to increase among those who became ill, especially 7–14 years old (k = 1), and among those who died – people over 65 years old (k = 1.6), and in inter-epidemic periods, the proportion of people aged 15 –64 years (k = 2) and children 0 –2 years (k = 1.5), and among the deceased – the proportion of people aged 15–64 years (k = 2.5). 
Conclusions. The predominant development of the COVID-19 epidemics in the autumn-winter seasons (6 versus 3), the high intensity of the epidemics of the autumn-winter season in terms of duration and incidence over the entire period and at its peak, and the presence of 4 inter-epidemic periods (3 of them in summer) indicate the seasonal nature of the COVID-19. 

Relevance. Meningococcal infection is characterized by highly variable epidemiology, unpredictable disease outcomes, difficulty in diagnosis, high mortality and disability rates, and a predominantly young child epidemic. 
Aim. To identify the epidemiological manifestations of meningococcal infection in the Russian Federation over an eleven-year observation period (2014–2024) and over a three-month period in 2025 (January–March). 
Materials and Methods. To analyze official incidence rates in the Russian Federation, Forms 1 and 2 of the State Statistical Reporting "Information on Infectious and Parasitic Morbidity" for 2014–2024 and Form 1 for January–March 2025 were used. In addition to official statistical reporting, an analysis of cases of generalized meningococcal infection (GFMI) was conducted based on data from reporting forms No. 1 of the Russian Reference Center for Monitoring Bacterial Meningitis (RCBM). 
Results. The average annual incidence rate (AAR) of generalized meningococcal infection (GMII) for 2014-2024 was 0.45 per 100,000 population. The Central Federal District (FD), and Moscow among the constituent entities of the Russian Federation, were most actively involved in the epidemic process. The incidence rate was predominantly among children under 1 year of age. The highest mortality rate was determined among children aged 0-17 years (AAR 0.27 per 100,000 population). Changes in the serogroup landscape of meningococcal strains were observed, with a shift from serogroup A, the leading serogroup in 2022, to serogroup W, the leading serogroup in 2023 and 2024. Against a background of relative epidemiological well-being, starting in December 2024 and over the first 3 months of 2025, the incidence rate in the Russian Federation increased by 4.4 times. Across regions, a steady increase in incidence was observed only in Moscow, where the rate increased 5.6-fold. Serogroup A was identified as the leading serogroup (up to 65 %). An analysis of incidence for the first three months of 2025 allows us to conclude that the meningococcal epidemic in Moscow reflects the epidemic in the Russian Federation as a whole. 
Conclusion. Given changes in the epidemiology of meningococcal infection, the identification of prerequisites for aggravating the epidemiological situation, the presence of significant migration flows, the predominant involvement of children under 1 year of age in the epidemic, and constant changes in the serogroup landscape of invasive meningococcal strains, it is necessary to expand the scope of vaccination within the regional immunization schedules and immediately include vaccination of children in the first year of life in the National Immunization Schedule using multicomponent vaccines.

Relevance. There are three zones of potential infection with dirofilariasis on the territory of the Russian Federation, the moderate–risk zone includes 18 subjects, and the high-risk zone includes 11 subjects. More than half of the cases of dirofilariasis in the Russian Federation occur in the Central Federal District (415 cases; 33.0 %) and the Volga Federal District (351 cases; 28.0 %).
Goal. To study the long-term dynamics and clinical and epidemiological features of the incidence of dirofilariasis in the population of the Russian Federation. 
Materials and methods. The report forms of Rospotrebnadzor «Information on infectious and parasitic diseases» for 2013–2023 and maps of the epidemiological survey of cases of dirofilariasis for 2019–2022 were used in the work. Epidemiological analytical and statistical research methods were used in the work. To describe the clinical data, a descriptive retrospective continuous study of the data from the epidemiological survey of dirofilariasis cases was conducted. 
Results. During the analyzed period (from 2013 to 2023), 1,248 cases of dirofilariasis were registered in the Russian Federation. The cumulative incidence of dirofilariasis was 0.078 0/0000, including 0.092 0/0000 among the adult population, which is significantly higher than 0.021 0/0000 among children. The long term dynamics was characterized by an uneven distribution over the years and ranged from 0.12–0.07 0/0000 with an average annual decrease rate of -3.1 %. The minimum incidence rates were recorded in 2020–2021 and amounted to 0.04 0/0000. The incidence rate of the adult population living in cities is 2 times higher than that of rural residents (0.089 0/0000 and 0.044 0/0000, respectively). Urban residents accounted for 86.0 % or 1,067 cases of diseases. 5 cases (3.8 %) were recorded in children aged 0-17 years. The incidence in children aged 0–17 years in 2023 was 0.020 0/0000 and remained stable compared to 2013–2022 (0.021 0/0000). A significant decrease in morbidity was recorded in adults 18 years and older (2020–2022 – 0.045 0/0000 versus 2013–2019, 2022–2023 (0.102 0/0000). The analysis of epidemiological examination maps of persons infected with Dirofilaria has been carried out. The average age of the infected was 42 years. The main group of patients with dirofilariasis is 30–39 years old and 40–49 years old (22.4 % and 20.7 %, respectively), to a lesser extent, young people aged 18-29 years (15.5 %). The proportion of children aged 0 to 17 years was 6.9 %. The structure of patients with dirofilariasis was dominated by women (65.0 %). The invasion is more often registered among urban residents (83.8 %). The largest number of cases of dirofilariasis was registered among unemployed people – 23.1 % and pensioners – 21.4 %. The proportion of cases among the working population was 36.8 %. The visual organs (upper and lower eyelids, eyeball, conjunctiva) were affected in 23.9 % of cases. In 36.8 % of patients, the parasite was localized in the head and neck, in 17.9 % – in the extremities, in 11.1 % – in the trunk and 6.0 % – in the genitals, 3.4 % – in the mammary glands. Communication with dogs is noted in 75.0 % of cases. Mosquito bites were not denied in 76.0 % of cases. When analyzing the epidemiological examination maps of individuals infected with Dirofilaria, infection was considered local in 70.0 % of cases. Imported cases were registered after visiting other countries: Kazakhstan, Cuba, Thailand, Sri Lanka, India, Abkhazia. 
Conclusion. Despite the fact that the incidence of dirofilariasis in the Russian Federation is characterized by a moderate downward trend, a number of factors contribute to maintaining the circulation of pathogens of this parasitosis and the emergence of new cases of infection

Measles and pertussis were widespread in all regions of the world in the pre-vaccine period. With the introduction of immunization, the incidence of these infections has sharply decreased, but the diseases continue to be reported in many regions. Understanding the dynamics of measles and pertussis co-proliferation is an important epidemiologic issue and provides the key implementing adequate and effective preventive measures. 
The aim of the research: to reveal integration-competitive relationships in the conjugated spread of measles and pertussis on the territory of Gomel region. The data of official records of measles and pertussis morbidity in the population of Gomel region for the period 1973–2024 were used in this work. For a more detailed characterization of the epidemic process manifestations, 4 time periods were identified, differing in the organization of vaccine prophylaxis: the period of single measles vaccination, the period of double measles vaccination, the period of measles elimination programme implementation and the modern period. Based on the analysis, it was revealed: 1. The long-term dynamics of measles incidence is in antiphase with the incidence of pertussis. 2. The intersection of the sinusoidal curves of the long-term dynamics of measles and pertussis incidence occurs every 10-16 years and does not depend on the level of vaccination. 3. Vaccination against measles and pertussis cough affects the trends in the development of epidemic processes of these infections. 4. The increase in measles and whooping cough incidence at the present stage is largely due to a decrease in the herd immunity of the population. 
Conclusion. Increasing the level of commitment to vaccination of the population and making changes to the National Immunisation Schedule are important tasks in ensuring epidemiological well-being.

Relevance. Streptococcus pneumoniae (pneumococcus) is one of the main causes of life-threatening infections, which leads to significant morbidity and mortality worldwide. Vaccination provides not only effective protection against pneumococcal infections, complications, and hospitalization, but can also help stabilize the public health system by reducing the incidence of respiratory infections, allowing you to focus on prevention, early detection, and treatment of chronic diseases. 
Аim. Аssess the coverage of vaccination against pneumococcal infection in patients with respiratory diseases in the Chelyabinsk region over the past 5 years.
Material and methods. The analysis included patients over the age of 18 with respiratory diseases registered in the Chelyabinsk region, according to Rosstat form No. 12 in the period from 2019–2023. Vaccination coverage was assessed on the basis of information entered into the unified medical information system of the Chelyabinsk region EMIAS BARS, section «Vaccination prevention». 
Results. The total coverage of vaccinated patients with respiratory pathology was 8 %, of which 40.8 % were patients with COPD. At the same time, 71.2 % of patients were vaccinated with PCV13, 28.8 % with PPV23. A low percentage of vaccinated patients was registered among patients with other respiratory diseases: with various forms of chronic bronchitis – 2.1 %, bronchial asthma – 3 %, postinfectious bronchiectasis – 14.6 %, interstitial lung diseases – less than 1 %. The highest incidence of communityacquired pneumonia is observed in patients with chronic obstructive pulmonary disease (COPD). 
Conclusion. These data indicate a lack of attention to the problem of vaccination against pneumococcal infection and a great potential for increasing coverage of the wider masses of patients, primarily from at-risk groups. Awareness of the population and primary care physicians should be a priority and include various tools aimed at popularizing vaccine prevention.

Introduction. Tuberculosis (TB) in children reflects the effectiveness of healthcare strategies in combating this infection within the entire population. Characterizing its trends retrospectively and currently allows for an assessment of future trajectories of the epidemiological situation regarding TB in a specific area. 
Objective. To evaluate the main epidemiological indicators of TB among children and adolescents in the Irkutsk region during a period of general improvement. 
Materials and methods. Data from statistical monitoring tuberculosis forms in children and adolescents from 2013 to 2023 were analyzed, along with factors that contributed to changes in the situation. 
Results. Total, 722 cases of tuberculosis have been registered in children (0–14 years old) and 270 cases in adolescents (15–17 years old) in the Irkutsk region. The observed long-term decline in TB incidence among children and adolescents occurs with varying intensity, and its slowdown during the COVID-19 pandemic and the subsequent period (2020–2023) is noted compared to 2013–2019: among children (7.2 % vs. 10.7 %) and adolescents (2.5 % vs. 8.1 %). The prevalence of TB in children 0–14 years old has decreased tenfold (from 42.30/0000 to 4.10/0000), while among adolescents aged 15–17 it has nearly tripled (from 51.20/0000 to 17.60/0000) and has been below average levels for the Siberian Federal District since 2018. There were still a significant number of MTB positive TB patients (980 cases) among the adult population of the Irkutsk region in 2023, including 515 with MDR TB, determining the existing risks of TB infection in children. 
Conclusion. Despite the slowed pace of improvement in the general epidemiological situation regarding TB, the Irkutsk region is reducing TB incidence rates among children and adolescents.

Relevance. Corynebacterium pseudodiphtheriticum has recently been increasingly considered as an etiologic agent of inflammatory diseases of various localizations, despite the fact that it is part of the microbiota of various biotopes of the human body. According to the literature, non- diphtheria corynebacteria and, in particular, C. pseudodiphtheriticum, are characterized by a dual nature, which is manifested by the presence of not only pathogenic, but also beneficial properties for the human body. In this regard, an important task is to differentiate colonization and infection caused by C. pseudodiphtheriticum, which may become possible when studying the genetic structure and virulence phenotype that determine the pathogenic effect on the human body. 
Aims: analysis of data from a study of the genome structure and phenotype characterizing the pathogenic and beneficial potential of phylogenetically closely related clinical isolates of C. pseudodiphtheriticum and C. propinquum from the oropharyngeal mucosa of healthy people. 
Materials and methods. Strains of C. pseudodiphtheriticum SX2, SX3, SX6 and C.propinquum SX4 were identified by mass spectrometry. Their whole genome sequencing and search for genes of pathogenicity, resistance to antimicrobial drugs (AMP), synthesis of amino acids, vitamins and terpenes were carried out. Virulence was determined on the model of wax moth larvae Galleria mellonella, sensitivity to AMP – by disk diffusion method, amino acid production – by tandem mass spectrometry. 
Results and discussion. It was found that all the studied isolates contain a wide range of polyfunctional genes regulating metabolism, pathogenicity (adhesion, survival inside macrophages, biofilm formation, etc.), resistance to AMP, as well as the rpf2 gene encoding the transition of corynebacteria from commensalism to parasitism. All the studied strains are low-virulent, produce glycine and valine, isolates of C. pseudodiphtheriticum SX2, SX6 and C.propinquum SX4 – alanine. The studied strains did not have a complete match in the pheno- and genotype of resistance to AMP. C. pseudodiphtheriticum SX6 belongs to the MDR category, showing phenotypic resistance to benzylpenicillin, ciprofloxacin and rifampicin. 
Conclusions. Thus, the duality of the nature of closely related strains of C. pseudodiphtheriticum and C.propinquum is characterized by the presence of a close relationship between pathogenic and beneficial properties. The implementation of the pathogenic potential of these microorganisms in the absence of true pathogenicity genes can occur with the activation of genes presumably associated with pathogenicity. This suggests that caution is needed when evaluating C. pseudodiphtheriticum (C.propinquum) strains as potential probiotics, even if they have a wide range of beneficial properties, given their ability to switch from commensalism to parasitism.

The study of the prevalence of dental pathology among small indigenous populations in the North is important for assessing the impact of dramatic social changes and shifts in traditional lifestyles on their health risks. This study aimed to investigate the prevalence of significant dental diseases and conditions among the indigenous and non-indigenous populations of the Krasnoselkupsky District of the Yamalo-Nenets Autonomous Okrug.

Materials and methods. A cross-sectional epidemiological study was conducted to assess the prevalence of major dental diseases and possible risk factors for their development in the Krasnoselkupsky District of the Yamalo-Nenets Autonomous Okrug. A dental examination was conducted on 400 individuals, and an anonymous survey was carried out with 121 respondents aged 18 to 76 years to collect information on the prevalence of risk factors for dental diseases and self-assessment of dental status.

Results and discussion. The point prevalence index of caries among the surveyed residents of the Krasnoselkupsky district was 97.3 per 100 people surveyed [95 % CI 95.1–98.5], compared to 96.1 per 100 people surveyed [95 % CI 91.8 –98.0] among the Selkups, and 98.0 per 100 people surveyed [95 % CI 95.3 –99.1] among local residents who do not represent this ethnic group. The  DMFCSR-index in the studied population group was 12.51 ± 0.93, indicating an average level of carious lesion intensity. The incidence of inflammatory periodontal tissue diseases was 59.5 per 100 examined (95 % CI 54.6–64.2). The prevalence rate for the nonindigenous population significantly exceeded that for the rural population (73.5 [95 % CI 67.6–78.6] versus 37.4 [95 % CI 30.2–45.3]). The survey results indicate that a low proportion of people consume potentially caries-causing products (59.5 % of respondents do not consume soda drinks).

Conclusion.  The study showed that caries and inflammatory periodontal diseases were less prevalent and less intense among the Selkup people than among the non-indigenous population of the Yamalo-Nenets Autonomous District. We assume that this difference is largely due to the Selkups' diet, which is characterised by relatively low consumption of carbonated drinks. Further epidemiological research is required to study the socio-cultural, microbiological and genetic factors influencing the manifestation of dental diseases among the Selkups, as well as to monitor the risk factors of this pathology.

Relevance. Acute respiratory infections (ARI) are a leading cause of morbidity and mortality in children worldwide. The COVID-19 pandemic has significantly influenced the circulation of other respiratory viruses. Understanding the interactions between SARSCoV-2 and other respiratory pathogens is crucial for predicting disease severity, improving diagnostic and treatment methods, and developing effective prevention strategies. 

Aims. This study aims to analyze changes in the circulation of respiratory viruses at different stages of the COVID-19 pandemic, investigate the prevalence and characteristics of viral and bacterial co-infections in children, and assess their impact on disease progression.

Conclusions.  At the initial stage of the COVID-19 pandemic, the incidence of respiratory viral infections declined, followed by a rapid resurgence after the lifting of restrictive measures. In children, COVID19 presents with milder symptoms than in adults and has a high proportion of asymptomatic cases. Mixed SARS-CoV-2 infections with other respiratory viruses are more common in younger children and do not significantly increase disease severity. However, secondary bacterial infections in children with COVID-19 substantially elevate the risk of severe disease progression.

Relevance. Breast milk is a vital source of nutrition and immune protection for newborns. The potential risk of transmitting various viral infections from the mother to the newborn during breastfeeding makes the issue of viral contamination in breast milk a relevant    area of research.

Aim. To present data on viruses found in breast milk and the associated health risks based on foreign scientific publications.

Conclusion. Despite the possibility of certain viruses being present in breast milk, existing scientific evidence confirms that, in most cases, the benefits of breastfeeding significantly outweigh the potential risks, especially when preventive measures are taken. Therefore, a comprehensive approach to assessing the risks and benefits of breastfeeding is essential for ensuring the health of both the mother and the child.