PECULIARITIES OF INFLUENZA ETIOLOGY DURING THE EPIDEMIC SEASONS OF 2018 AND 2019 YEARS IN THE KHABAROVSK REGION

Abstract

An interpretation of etiological data concerning two epidemic elevations of influenza incidence was conducted in the Khabarovsk region. Influenza and acute respiratory infection (ARI) incidence elevated gradually in the Ist and IInd quarter of the 2018 year. Еxceedance of epidemic threshold in regard with “control” in Khabarovsk city was registered only for two weeks. The etiology of breakout was conditioned by co-circulation of three influenza virus serotypes: A/H3N2/, B – Yamagata line and A/H1N1/pdm09. B and A/H3N2/ virus types were dominant. B influenza viruses comprised 66.1%, A/H3N2/ – 28.5%, A/H1N1/pdm09 – 5.4%. Comparison of the observed viruses circulation intensity in the Khabarovsk region and Russian Federation revealed lesser frequency detection of A/H1N1/pdm09 in the Khabarovsk region – by 5.8 times. At the same time, two other serotypes were circulating more extensively. During the first quarter of the 2019, the etiology of subsequent influenza incidence elevation was caused by dominating A/H1N1/pdm09 virus type (93.7%) when A/H3N2/ totaled 6.3%. Distinctive differences between the Khabarovsk region and Russian Federation indices were also revealed during the second elevation of influenza incidence. The A/H1N1/pdm09 exceeded average weekly incidence registered in the Russian Federation by 1,9 times when A/H3N2/ virus was registered sporadically and the region average weekly incidence was lower by 6.6 times. An analysis of clinical manifestations of the influenza was investigated as well as influenza viruses and other acute respiratory viral infection pathogens mixt-infection detection frequency. It is suggested to consider the differences in influenza etiology in constituent entities when constructing epidemic projections and organization of preventive measures against influenza.