Dependence of COVID-19 epidemic process intensity on circulation of SARS-CoV-2 genovariants was evaluated in nine supervised regions of the Far Eastern Federal District during the first 39 calendar weeks (from January 2 to October 1) of the year 2023. COVID-19 epidemic process in all nine supervised regions had common patterns despite some differences in geographical position, population size and density of the constituent entities. The epidemic continues to be characterized as a wave-like curve, however periods of increase of incidence become shorter and number of COVID-19 cases are several times lower compared to same period last year. All nine regions of the Far Eastern Federal District showed a decrease in mortality rate due to COVID-19 despite an increase in COVID- 19 incidence during the first thirty-nine weeks of the year 2023, which indicates a decrease of the disease severity. All described peculiarities were associated with widespread circulation of SARSCoV-2 Omicron variant. Current strain underwent several genetic changes during the time of conducted research. They were revealed by molecular genetic monitoring of SARS-CoV-2 variability.

The Khabarovsk krai is a disadvantaged region of the Far Eastern Federal District in terms of the enterovirus infection incidence. Every year in the region there is a seasonal increase in cases of enterovirus infection (EVI) with the registration of foci of group morbidity among children. The article presents data from an analysis of the EVI incidence in the Khabarovsk krai from January to August 2023 and the results of molecular genetic monitoring of circulating non-polio enteroviruses during this period.

Epidemiological analysis of rotavirus infection incidence was carried out and results of molecular genetic monitoring of rotaviruses circulating in the Khabarovsk krai during year 2022 were analyzed. It was established that rotavirus infection incidence rate in the year 2022 was slightly higher than longterm average level calculated for the period of observation that included years 2010–2019 (92.3 and 90.5 per 100 000 population, respectively). Predominance of preschool children was revealed among infected patients. Four outbreaks of rotavirus infection were registered in children's educational institutions in the year 2022. Molecular genetic analysis of pathogens found in foci of the outbreaks revealed circulation of three prevalent G-genotype rotaviruses: G9, G4 and G3. Phylogenetic analysis of rotavirus A genotype G9 indicated their possible importation from the countries of Southeast Asia when analysis of rotavirus A genotype G3 strains allowed to classify them as reassortants. Other rotavirus strains obtained from the foci of the disease outbreaks located the Khabarovsk krai were typed as P[8]-3 lineage in accordance with P-genotype strains. Regular monitoring of rotaviruses carried out against the background of continuous epidemiological analysis of incidence makes it possible describe the epidemic process of rotavirus infection in a specific territory more accurately.

Serological and molecular-genetic analysis was performed for 39 samples of blood serum/plasma obtained from patients diagnosed with chronic viral hepatitis residing in the territory of the Sakhalin oblast. HBV DNA was revealed in 7 out of 18 samples of blood plasma of the patients with revealed serological markers of hepatitis B virus. HBV genotype D including subgenotypes D1, D2, D3 was detected in 5 samples. HBV subtype A was revealed in 2 out of 7 samples. HCV RNA was isolated in 24 out of 32 (68.6±5.5%) blood plasma samples positive for HCV antibodies that were detected with ELISA. Molecular-genetic survey of hepatitis C virus revealed circulation of subtypes 1a, 1b, 2a and 3a with predominance of subtype 3a.

Viral hepatitis continue to be a global health problem due to the significant morbidity and mortality associated with these infections.The research established that prevalence of HBsAg, a serological marker of viral hepatitis B (HBV), indicating active infectious process, among population of the Khabarovsk Territory, totaled 0.55%, anti-HBc - 18.55%, anti-HCV - 4.11 % . No anti-HDV were detected.Detection rate of viral hepatitis markers between different age groups as well as between men and women did not have any differences except for anti-HBc. The frequency of anti-HBc registration among the age group of 18-29 years old turned out to be lower than estimated average and amounted to 2.0%, should be noted that no HBsAg was detected among them. Anti-HBc was found to be higher among people aged 70 years in comparison with the estimated average and totaled 34.0 %. Anti-HBc were detected more often among women (20.55%) compared to men (14.18%). Almost no age and gender peculiarities of anti-HCV prevalence were revealed with one exception. Men aged 30-39 years (10.2%) had higher detection rate of anti-HCV compared to women of the same age (1.98%). HBsAg-negative hepatitis B was detected in one case (0.62%) among anti-HBc-positive samples. Anti-HDV and HDV RNA were not detected in any of the HBsAg-positive samples.

HIV epidemic continues to be a pressing medical and social issue both in Russia and in the Far Eastern Federal District. The number of HIV-infected people in the Far Eastern Federal District reached 52 062 cases as of 01.01.2023. At the same time prevalence, growth rate has decreased and totaled 425.1 per 100 thousand population in the year 2023. HIV-epidemic in the Far Eastern Federal district is in a concentrated phase. The coverage of HIV testing in the district's population totaled 30.6%. Most cases of HIV-infection were acquired sexually and were associated with heterosexual contact. A total number of 81.1%of people living with HIV were registered for regular medical check-ups and 67.8% of all people living with HIV received antiretroviral therapy. The article presents results of epidemiological analysis carried out in order to reveal development of HIV epidemic features in 11 territories of the Far Eastern Federal District during years 2018-2022.

Epidemiological significance of echinococcosis is determined by its wide distribution, severe course of infection with multiple lesions of various organs that lead to long-term impairment, disability and lethal outcome. The article presents results of a seroepidemiological survey of population of the Khabarovsk krai, Jewish Autonomous and Amur Oblasts for the presence of antibodies against antigens of Echinococcus granulosus. Obtained results may indicate a discrepancy between recorded and actual morbidity rates of the population with this helminthiasis. Taking into account absence of specific clinical manifestations of cystic echinococcosis at early stages of the disease, it is advised to expand seroepidemiological surveillance.

One of the rare complications of infectious mononucleosis is a rupture of the spleen. The article presents a brief literature review and analysis of a clinical case of a ruptured spleen in a patient with infectious mononucleosis caused by the Epstein-Barr virus. The patient had clinical and laboratory parameters characteristic of infectious mononucleosis: fever, tonsillitis, nasal breathing disorders, generalized lymphadenopathy, hepatosplenomegaly, leukocytosis, lymphocytosis. The diagnosis was confirmed serologically. This patient developed intense abdominal pain, a state of shock, and after a while there was tension of the muscles of the anterior abdominal wall and a positive symptom of Shchetkin-Blumberg. In the general blood test, the number of red blood cells and the level of hemoglobin decreased. The revision of the abdominal organs revealed a two-stage rupture of the enlarged spleen with a hematoma in the rupture cavity and active bleeding, as well as decapsulation of the lower pole. Splenectomy and autotransplantation of splenic tissue in the area of the spleen bed were performed.

The purpose of this review was to summarize literature data and our own observational studies on the etiology, epidemiology and prevention of polio- and enterovirus (non-polio) infection. To date, the history of combat against such a dangerous disease as poliomyelitis was mostly presented by evaluation of vaccine prevention and certification of eradication of wild poliovirus transmisson in the world regions. A perspective of more profound study of other non-polio enteroviruses has appeared during post-certification period and surveillance of enterovirus (non-polio) infections became an integral part of poliovirus surveillance. In recent years, molecular genetic research methods have been widely used to identify a wide variety of polioviruses, including wild and vaccine-associated strains as well as non-polio enteroviruses, especially those with a high epidemic potential for spread among the world population. Such genetic diversity of pathogens can be used in predicting epidemic situation especially associated with the risk of cross-border importation of specified pathogens.

Diseases and conditions caused by human herpes virus type 6 are widespread, clinically diverse, often severe and require differential diagnosis and appropriate treatment. The literature review presents the pathogenetic, clinical and laboratory aspects of these diseases and conditions. Human herpes virus type 6 has two subtypes 6A and 6B, which differ from each other in biological properties, epidemiological characteristics, tropism for certain cells and the spectrum of pathological changes caused. Subtype 6A is involved in the development of epilepsy, multiple sclerosis, graftversus-host disease in organ recipients, and the progression of HIV infection. Primary infection with subtype 6B may result in roseola, acute fever without rash with febrile seizures, or encephalitis. Human herpes virus type 6 is capable of integrating into telomeres of somatic chromosomes, which leads to its hereditary transmission. Human herpes virus type 6 has protein U94, which contributes to the latency of the virus and suppresses the immune response.

A retrospective epidemiological analysis of Q fever incidence that was conducted for the whole territory of the Russian Federation during years 2013 - 2022 revealed annual variation in the number of infection cases - from 8 cases of infection (0.0050/0000) in 2020 to 286 cases (0.190/0000) in 2019., a long-term average totaled 0.070/0000. Registration of Q fever incidence in different Federal districts and constituent entities of the Russian Federation was uneven. The largest number of the disease cases were registered in the Stavropol krai, Astrakhan, Voronezh, and Rostov oblasts. Q fever incidence in Astrakhan oblast was ranked highest among all constituent entities of the Russian Federation. No cases of the infection were detected in two Federal districts during the specified period of observation – in the Ural and Far Eastern Federal districts. It has been established that Q fever incidence in other Federal districts of the Russian Federation was recorded during all months of the year with highest indices registered from May to August. Patients were most often presented by workingage men whose work was related to agricultural labor including animal care. A necessity of introduction of additional surveillance measures for monitoring Q fever incidence among human population as well as establishing prevalence of the pathogen among animals in the future is advisable.

Monitoring the abundance, species composition and infection rate of tick-borne infections (TBI) carriers is an integral element of epidemiological surveillance over this group of diseases. The article presents results of evaluation of removed from humans ixodid ticks infection rate in the Khabarovsk krai from 2017 to 2023. The highest rates of tick attacks on humans and infection rate with TBI pathogens were recorded for I. persulcatus species, which determines its high epidemiological significance. The results of the study confirm a necessity of compliance with TBI nonspecific prevention measures during the period of ixodid ticks activity when visiting forests, park areas, natural landscape conservation areas.