PECULIARITIES OF THE INFLUENZA EPIDEMICS DURING 2015–2016, 2016–2017 AND 2017–2018 SEASONS IN THE REPUBLIC OF SAKHA (YAKUTIA)

We analyzed the epidemiological situations on influenza and acute respiratory viral infections during the 2015–2016, 2016–2017 and 2017–2018 epidemic seasons in the Republic of Sakha (Yakutia). The 2015–2016 and 2016–2017 epidemic seasons differed from the previous ones by a rather high intensity of the epidemic process, moderate duration of the epidemic awareness with a two-wave pattern of the course, high morbidity of the population at the epidemic peak and the absence of the disease’s severe forms in those vaccinated against influenza. During the 2015–2016 epidemic season, the influenza A (H1N1) virus was the dominant pathogen in Yakutia. During the 2016–2017 epidemic season, the first morbidity awareness was caused by the influenza A (H3N2) virus, the second morbidity awareness was caused by the influenza B virus. In contrast to previous two seasons the 2017–2018 epidemic season is characterized by lower intensity, a significant morbidity decrease of influenza and acute respiratory viral infections in different age groups of the population and a low level of influenza viruses' circulation. Influenza A (H3N2) virus dominated and joined influenza B virus circulation was registered subsequently during the 2017–2018 epidemic season.