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.

In late 2019, there were reports of an outbreak of infection caused by a new strain of beta coronavirus SARSCoV-2, the WHO identified the disease as coronavirus disease 2019 (COVID-19). In Tatarstan, the first case of COVID-19 was diagnosed on March 16, 2020, it was an imported case from France. The period of increase in the incidence lasted during the 12th to the 19th week, when the highest rate was recorded, amounting to 16.7 per 100 thousand population. Subsequently, a statistically significant decrease in the incidence was noted. Seroprevalence study was conducted at week 27 (8th week of decline of morbidity).The purpose of the seroepidemiological study was to measure the level and to identify the structure of herd immunity against the SARS-CoV-2 virus among the population of the Republic of Tatarstan during the rapid spread of the COVID-19 outbreak.Materials and methods. The selection of volunteers for the study was carried out by the method of questionnaires and randomization by random sampling. The exclusion criterion was active COVID-19 infection at the time of the survey. 2,946 people were examined for the presence of specific antibodies to SARS-CoV-2. The age of the surveyed volunteers ranged from 1 year to 70 years and older.Results. The results of the study showed that in the Republic of Tatarstan during the period of COVID-19 incidence, there was a moderate seroprevalence to SARS-CoV-2, which amounted to 31.3%, against the background of a high frequency (94.5%) of asymptomatic infection in seropositive individuals who did not have a history of past COVID-19 disease, positive PCR result and ARVI symptoms on the day of the examination. The maximum indicators of herd immunity were established in children aged 7–13 years (42.0%), children 14–17 years old (40.3%), with a simultaneous decrease in seroprevalence in persons aged 70 and older (24.0%). In different regions of the Republic of Tatarstan, there was a wide variation in seropositivity results from the minimum in the Zainsky district (8.6%) to the maximum in the Arsky district (74.3%). In 21 out of 38 surveyed districts, the results were unrepresentative due to the small sample size. In COVID-19 convalescents, antibodies are produced in 83.3% of cases. In persons with a positive result of the PCR analysis carried out earlier, antibodies were detected in 100% of cases. Among the volunteers who had contact with patients with COVID-19, the proportion of seropositive is 37%Conclusion. The dynamics of seroprevalence among the population of the Republic of Tatarstan can be qualified as positive, the results obtained can be used to develop a forecast for the development of the epidemiological situation, as well as to plan measures for specific and non-specific prevention of COVID-19.

In consequence of epizootiological investigation, differentiated has been Kazan territory according to the potential epidemic hazard levels; determined is the abundance of carriers and vectors of natural-focal infection agents in and around the territory of the Summer Universiade-2013; substantiated is the scope of preventive measures (disinfection, deratization, desinsection), as well as their frequency and coverage area. Timely detection of the regions with expressed epizootic potential growth has made it possible to carry out prophylactic activities and reach an epidemic-hazard-lowering effect as regards particular territories of the natural and anthropourgic infectious disease foci. Further on, validated has been disinfection as part of specific prophylaxis and as a basic measure for elimination of risks of the population exposure to natural-focal infections directly during the mass event.

РефератОбеспечение санитарно-эпидемиологического благополучия населения в период подготовки и проведения массовых мероприятий с международным участием -одна из важнейших задач обеспечения безопасности го-сударства. Прибытие на массовые мероприятия большого количества участников, официальных лиц и гостей из различных стран мира всегда связано с формированием условий для возникновения эпидемиологического риска в связи с возрастающей нагрузкой на санитарно-гигиеническую инфраструктуру мест их проведения и кратко-временным увеличением плотности населения на ограниченной территории. Подготовка и проведение массовых мероприятий проводятся на местном и международном уровнях и требуют координации различных заинтересо-ванных структур и ведомств страны-организатора, а также взаимодействия с другими странами и международ-ными организациями. Система мероприятий по обеспечению санитарно-эпидемиологического благополучия на-селения на территории нашей страны включает эпидемиологический надзор и контроль (система мониторинга и анализа), контроль санитарного состояния и безопасности окружающей среды, мероприятия по локализации и ликвидации чрезвычайных ситуаций санитарно-эпидемиологического характера. Проблема обеспечения сани-тарно-эпидемиологического благополучия населения научно структурирована в виде следующих направлений: санитарной охраны территории; эпидемиологического надзора за природно-очаговыми зоонозными и другими опасными инфекционными болезнями; предупреждения и противодействия чрезвычайным ситуациям санитар-но-эпидемиологического характера, возникающим самостоятельно, а также как следствие стихийных бедствий и антропогенных катастроф. Прошедшие XXVII Всемирная летняя Универсиада (2013) в г. Казани, XXII Олим-XXII Олим-Олим-пийские игры и XI Параолимпийские зимние игры (2014) в г. Сочи показали готовность служб, ответственных за обеспечение санитарно-эпидемиологического благополучия населения, к проведению крупных спортивных мероприятий. Актуальным представляется дальнейшее изучение опыта зарубежных стран, обобщение полученно-го опыта проведения массовых мероприятий с международным участием на территории нашей страны с целью разработки научного обоснования и принятия эффективных управленческих решений по обеспечению санитар-но-эпидемиологического благополучия населения.Ключевые слова: массовые мероприятия с международным участием, эпидемиологический риск, санитарно-эпидемиологическое благополучие. CURRENT PROBLEMS OF SURVEYING SANITARY AND EPIDEMIOLOGICAL WELL-BEING AT PUBLIC EVENTS WITH INTERNATIONAL PARTICIPATION M.A. Patyashina, L.А. Balabanovа Federal Service for Surveillance on Consumer Rights Protection and Human Well�being Branch at Republic of Tatarstan, Kazan, RussiaProviding public sanitary and epidemiological welfare while preparing and holding public events with international participation is one of the prime tasks in ensuring state security. When large numbers of participants, officials and guests from different countries of the world arrive for public events, these conditions are always associated wit...