Эпидемиологическая характеристика ОРВИ и гриппа на территории Казахстана в эпидемические сезоны с 2018 по 2022 год

Abstract

One of the most important medical and socio-economic problems worldwide is the incidence of influenza and acute respiratory viral infections (ARVI). The urgency of the problem is due to their widespread prevalence, economic costs, the high probability of a complicated course and exacerbation of chronic non-communicable diseases, the variability of viruses, and the formation of bacterial-associated respiratory diseases against their background. In recent years, the simultaneous circulation of influenza A(H1N1), A(H3N2) and type B influenza viruses has been observed during the epidemiological season. The COVID-19 pandemic has affected the situation of the incidence of ARVI and influenza in the Kazakhstan. Objective. To assess the epidemic situation in Kazakhstan during the epidemic seasons 2018–2019, 2019–2020, 2020–2021, and 2021–2022 and to identify influenza pathogens circulating among the population. Materials and methods. Epidemiological surveillance for ARVI and influenza in Kazakhstan includes several components. The routine system of registering ARVI cases based on appeal is carried out by organizations providing primary medical care. In 2008, epidemiological surveillance for ARVI and influenza was supplemented with sentinel epidemiological surveillance. Sentinel surveillance for influenza, ARVI, influenza-like illness, and SARS is carried out year-round, and the incidence of influenza in outpatients and inpatients is monitored. Records are kept of all requests for medical care in age groups of 0–4, 5–14, 15–29, 30–64, 65 years and older. During the research, the results of regular monitoring in the surveillance system for influenza, ARVI, influenza-like illness, and SARS in four seasons of ARVI and influenza incidence (epidemic seasons from 2018–2019 to 2021–2022, from 40 weeks of the first year to 20 weeks of the second year) were used. Data on the incidence of ARVI and influenza, the results of laboratory tests of the weekly monitoring of the Reference Laboratory for the Control of Viral Infections of the Scientific and Practical Center for Sanitary and Epidemiological Expertise and Monitoring and 16 regional virological laboratories of branches of the National Center for Expertise, combined into a single Information system "Tracking ARVI/influenza/pneumonia", were taken into account. During the study period, coverage in the Republic of Kazakhstan amounted to 2,408,525 cases of ARVI and influenza, including 93,233 hospitalizations. A total of 39,251 samples were examined for influenza, of which 5,553 PCR tests were positive. Sampling for sequencing is carried out after PCR, while samples with a high concentration of viral RNA (Сt ≤25) are taken. Sequencing methods are used for genotyping of influenza viruses. The research methods also included a molecular genetic study of samples from patients with ARVI and influenza. Results. The highest incidence rates of ARVI and influenza were observed in the epidemic season of 2021–2022, with their maximum levels recorded from the 40th to the 51st week and from the 3rd to the 5th week. In the epidemiological seasons 2018–2019 and 2019–2020, the influenza A(H1N1)pdm09 virus dominated, followed by the influenza A(H3N2) virus and the active circulation of the influenza B virus. In the 2020–2021 epidemiological season, 6,564 PCR studies of samples for the presence of the SARS-CoV-2 virus were conducted in the Republic of Kazakhstan, of which 421 (6%) were positive samples, and in the 2021-2022 epidemiological season – 820 (4%). Conclusion. The results of the analysis show that the circulation of influenza and other ARVI pathogens in the epidemiological season continues to play a leading role in the etiology of respiratory viral infections. Key words: influenza viruses, SARS-CoV-2 virus, influenza, morbidity, ARVI, epidemiological situation