The SARS-CoV-2 pandemic, which came to Russia in March 2020, is accompanied by morbidity level changes and can be tracked using serological monitoring of a representative population sample from Federal Districts (FDs) and individual regions. In a longitudinal cohort study conducted in 26 model regions of Russia, distributed across all FDs, we investigated the distribution and cumulative proportions of individuals with antibodies (Abs) to the SARS-CoV-2 nucleocapsid antigen (Ag), in the period from June to December 2020, using a three-phase monitoring process. In addition, during the formation of the cohort of volunteers, the number of seropositive convalescents, persons who had contact with patients or COVID-19 convalescents, and the prevalence of asymptomatic forms of infection among seropositive volunteers were determined. According to a uniform methodology, 3 mL of blood was taken from the examined individuals, and plasma was separated, from which the presence of Abs to nucleocapsid Ag was determined on a Thermo Scientific Multiascan FC device using the “ELISA anti-SARS-CoV-2 IgG” reagent set (prod. Scientific Center for Applied Microbiology and Biotechnology), in accordance with the developer’s instructions. Volunteers (74,158) were surveyed and divided into seven age groups (1–17, 18–29, 30–39, 40–49, 59–59, 60–69, and 70+ years old), among whom 14,275 were identified as having antibodies to SARS-CoV-2. The average percent seropositive in Russia was 17.8% (IQR: 8.8–23.2). The largest proportion was found among children under 17 years old (21.6% (IQR: 13.1–31.7). In the remaining groups, seroprevalence ranged from 15.6% (IQR: 8–21.1) to 18.0% (IQR: 13.4–22.6). During monitoring, three (immune) response groups were found: (A) groups with a continuous increase in the proportion of seropositive; (B) those with a slow rate of increase in seroprevalence; and (C) those with a two-phase curve, wherein the initial increase was replaced by a decrease in the percentage of seropositive individuals. A significant correlation was revealed between the number of COVID-19 convalescents and contact persons, and between the number of contacts and healthy seropositive volunteers. Among the seropositive volunteers, more than 93.6% (IQR: 87.1–94.9) were asymptomatic. The results show that the COVID-19 pandemic is accompanied by an increase in seroprevalence, which may be important for the formation of herd immunity.

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

На протяжении многих лет одной из наи-более опасных и широко распространенных сре-ди природно-очаговых болезней в Российской Федерации (РФ) остается клещевой вирусный энце-фалит (КВЭ) [1, 2,[4][5][6][7][8][9].Цель работы -анализ эпидемиологической об-становки по КВЭ и мер, осуществленных по профи-лактике болезни на территории страны в 2015 г., про-гноз заболеваемости населения на 2016 г.Анализ эпидемиологической ситуации в 2015 г. основан на материалах еженедельного оперативно-го мониторинга, осуществляемого учреждениями Роспотребнадзора в субъектах РФ, представляемых в Федеральную службу по надзору в сфере защиты прав потребителей и благополучия человека и в Референс-центр по мониторингу природно-очаговых инфекци-онных заболеваний бактериальной и вирусной этио-логии ФКУЗ «Иркутский научно-исследовательский противочумный институт» Роспотребнадзора. Статистическая обработка проведена стандартными методами вариационной статистики с применением программы Excel.По данным мониторинга, в эпидемический се-зон 2015 г. в РФ зарегистрировано 2116 больных (1,45 о / оооо ) и 24 летальных исхода (2014 г. -23) от КВЭ. По сравнению с 2014 г. количество заболевших увеличилось на 138 человек (6,5 %), что свидетель-ствует об ухудшении эпидемиологической ситуации на фоне наблюдающегося с начала ХХI века тренда на снижение эпидемических проявлений КВЭ [1, 6, 7, 8]. Необходимо подчеркнуть, что рост заболе-ваемости наблюдался во всех эндемичных по КВЭ Analyzed has been epidemiological situation and measures, performed for prophylaxis of tick-borne viral encephalitis in the territory of Russia in 2015. It is shown that the number of humans bitten by ticks increased in the majority of the constituent entities of the country. But specific and nonspecific preventive operations in 2015 were realized to a lesser extent as compared to 2014. Along with the natural factors, it might be the reason for increase in human tick-borne viral encephalitis morbidity rates. In total, 2116 patients with tick-borne viral encephalitis and 24 lethal cases were registered in the country. On the basis of the data regarding tick-borne viral encephalitis (TBVE) incidence rate among the population across the Federal Districts of Russia over a period of 2009-2015, forecasted have been intensive indicators of the clinical forms' manifestations for 2016. TBVE morbidity rate in RF will amount to (1.90 ± 0.21) о /оооо. With 95 % probability it will be retained within a range of 1.4-2.4 о /оооо.

Objective of the study was to monitor the spread of cholera in the world, in the CIS countries and in Russia with an assessment of risks and emergencies that contribute to the activation of the epidemic process. Despite the downward trend in the global incidence rate of cholera during the period between 2010 and 2019, epidemics and major outbreaks occurred in 96 countries. WHO has reported 2013 imported cases of cholera to countries in Asia, the Americas, including the Caribbean, Europe, and Australia with Oceania; cholera-endemic administrative territories are identified in 24 countries. According to WHO, cholera burden reduction in Asia and Africa is associated with large-scale vaccination. During epidemiological surveillance of cholera, 705 strains of V. cholerae O1 and O139 serogroups were isolated from surface reservoirs in 26 constituent entities of the Russian Federation, including 10 strains of V. cholerae O1 ctxA+tcpA+, 35 strains of V. cholerae O1 ctxA–tcpA+, 655 strains of V. cholerae O1 ctxA–tcpA– , and five strains of V. cholerae O139 ctxA–tcpA–. Identification of strains with unique, previously unknown INDEL genotypes testifies to their imported nature. The forecast for cholera in the world for 2020, given the proven high degree of epidemic process activation at the expense of social and environmental risks caused by emergencies of different origin, the presence of endemic foci, infection import and other risk factors is unfavorable. For Russia, the forecast for cholera will be determined by the presence of external risks created by the ongoing 7-th pandemic, possible importation of infection to constituent entities of the Russian Federation that differ by the types of epidemic manifestations.

The aim of the study is to summarize the results of a study of seroprevalence of children to SARS-CoV-3, obtained during the implementation of the Rospotrebnadzor program to assess seroprevalence to the NC antigen SARS-CoV-2 of the population of 26 regions of the Russian Federation, conducted during the COVID-19 epidemic in 2020. Research methods: the study of seroprevalence in 26 model territories of the Russian Federation was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of the St. Petersburg Pasteur Institute of Epidemiology and Microbiology. The method provided for the formation of a group of volunteers in a model federative entity, including children aged 1–17 years, in which the presence of antibodies to the SARS-CoV-2 nucleocapsid was determined in venous blood plasma by the enzyme-linked immunosorbent assay (ELISA). The examination of volunteers was carried out in 3 stages: June-August, September-October, December. Results: the study found that in most of the areas surveyed, children had a higher level of seroprevalence than adults. It is shown that high seroprevalence is accompanied by statistically significant decrease in morbidity (p0.05). The analysis of seroprevalence at all three stages revealed at least 3 variants of its dynamics: 1) continuous growth of seroprevalence in parallel with the development of the epidemic process; 2) an episodic change in the periods of increase and decrease in the level of seroprevalence; 3) a continuous decrease in seroprevalence at the level of the epidemic process. Comparative determination of seroconversion levels in three age groups – 1–6, 7–13 and 14–17 years – revealed no statistically significant differences between these age groups have been identified. Conclusion: children aged 1–17 years in most of the surveyed territories of the Russian Federation have a higher seroprevalence to SARS-CoV2 than adults. The increase in seroprevalence in children is accompanied by a decrease in the incidence of COVID-19.