Objective was to investigate the SARS-CoV-2 collective immunity status of the population of Belarus within the context of the COVID-19 pandemic. Materials and methods. The work was carried out according to the methodology for assessing SARS-CoV-2 population immunity, developed by Rospotrebnadzor Russia and the Ministry of Health of Belarus with the participation of the St. Petersburg Pasteur Institute, taking into account WHO recommendations. The Bioethics Committee of Belarus and the local ethics committee of the St. Petersburg Pasteur Institute approved the study. Selection of participants was carried out using a questionnaire method and online technology (internet, cloud server). Volunteers were randomized into seven age groups (years of age): 1–17; 18–29; 30–39; 40–49; 50–59; 60–69; and 70+. Regional randomization ensured proportional representation of volunteers from each region, and no more than 30 people were included from one enterprise. In accordance with manufacturer instructions, blood plasma samples were analyzed for: IgG antibodies (Abs) to the SARS-CoV-2 nucleocapsid (Nc) using a quantitative ELISA test system; and IgG Abs to the receptor binding domain (RBD) of the SARS-CoV-2 S (spike) surface glycoprotein using a qualitative ELISA test system. Statistical processing was carried out using Excel 2010 and other software. Statistical differences were designated as significant when p < 0.05, unless otherwise indicated. Results. The level of seroprevalence, in terms of Abs to Nc among the Belarusian population, was 38.4% (95% CI 37.6–45.4). The highest Ab levels were found among individuals in older age groups (50-70+ years old). The lowest were found in children 1–17 years old and in young people 18–39 years old The distribution of seroprevalence across Belarusian regions was relatively homogeneous, with the exception of the Minsk Region, where a statistically significant decrease in the indicator was noted. In terms of profession, the largest share of seropositive individuals was found among transportation workers; the smallest was found in business. The moderate COVID-19 incidence has not led to a dramatic increase in the number of contacts. The base reproduction number (R0) was 1.3. In the Republic of Belarus, there was a moderate level of asymptomatic COVID-19 among seropositive individuals (45.3% [95% CI 44.0–46.7]). This form of infection was observed most often among children aged 1–17 years old (65.0% [95% CI 61.3–68.6]). In parallel with seroprevalence assessment, SARS-CoV-2 vaccination was carried out. We used two vaccines: Gam-COVID-Vac (also known as Sputnik V, developed by Gamaleya National Center for Epidemiology and Microbiology, Russia); and BBIBP-CorV (Sinopharm, PRC). Vaccination against SARS-CoV-2 was accompanied by an increase in the level of anti-RBD Abs (95% [95% CI 94.7–96.7]). Taking into account the vaccination of a subset of the population with BBIBP-CorV, the overall herd immunity, inferred from the analyzed indicators (presence of anti-Nc or anti-RBD Abs), was 47.1% (95% CI 46.3–48.0). Conclusion. COVID-19 in Belarus was characterized by a moderately pronounced course of the epidemic process. The threshold level of herd immunity to SARS-CoV-2 has not yet been reached, as a result of which the conditions for progression of the epidemic remain.

Outlined is the analysis of epidemiological and epizootiological situation on Crimean hemorrhagic fever (CHF) in the south of the Russian Federation in 2011. Discussed are the causes of nosocomial outbreak of CHF at the Salsk district central hospital, the Rostov Region. Prognostication on CHF situation for 2012 is made based on the epizootiological monitoring.

The study in question of the structure and content of international cooperation in the sphere of sanitary-and-epidemiological welfare of the population in its various formats – on the UN, WHO, “G-8”, CIS, EurAsEC, SCO, and BRICS levels, as well as within the frames of bilateral relations between the Russian Federation and Republic of Kazakhstan – has made it possible to develop a model of international intercourse organization characterized by such functional features as assessment of the epidemiological situation peculiarities and IHR implementation status, realization of global strategy for infectious diseases control, systemic modernization of methodology, technologies, materials-and-equipment resources as well as human assets and production of medical immune-biological preparations (MIBP), stationary network and mobile complexes for emergency response in order to level the interstate potentials for the provision of effective prevention, detection and monitoring over emergency situations in the sphere of sanitary-and-epidemiological welfare of the population (ES). Top-priority in the list of the ESs is given to novel emerging infectious diseases control as it primarily demands improvement of the informational–and–analytical prognosis–modeling base within the frames of epidemiological surveillance system and sanitary protection of the state territories. Great need in such type of projects is substantiated based on the examples of Crimean-Congo hemorrhagic and West-Nile fevers control. Nevertheless, for the realization of the model, coordinating functional authority/agency is required.

A set of documents concerning biological safety at the institutional level is prepared and put in to practice. Three levels of specialists` admission for works with pathogenic biological agents of the I-IV groups have been developed, substantiated and introduced. Considered are the variants of execution of coupled (simultaneous) work with PBA of different groups. The statement on control of disinfectants received by the institution defines the order of control execution as regards newly received disinfectants and correspondence of disinfectants` working solutions in the laboratories to the requirements of sanitary regulations. Demonstrated is practicability of the assessment of protective efficacy of air-cleaning filters in the exhaust ventilation systems of "contaminated" area rooms in the laboratories carrying out the works with PBA using bacterial aerosol and physical method.