Sominina Anna
Research Institute of Influenza of the Ministry of Healthcare of the Russian Federation, Russian Federation
Title: Analaysis of the features of the influenza epidimic 2015-2016 in russia and possible factors that defined its severity
Biography
Biography: Sominina Anna
Abstract
The unusalrapid growth of influenza activity caused by A(H1N1)pdm09 viruses was registered simultaneously in number of geographically remote areas of Russia during the season 2015-2016.Intensity of epidemic was much higher in comparison with previous four years. Significant increase of incidence rate,hospitalization and number of lethal cases observed since week 3,2016.peak of epidemic registered already on the week 5.Such a rapid speard of the epidemic indicated high transmission level of the virus. Many factors can influence this process including changes in the antigenic properties of virus HA, certain changes in internal genes, as well as decrease of population immunity . Antigenic analysis of viruses circulated showed that all A(H1N1)pdm09 viruses were antigenically related to A/California/07/09. The contribution of the rest influenza and B viruses last season was insignificant: proportion of isolated influenza A(H1N1)pdm09, A(H3N2) and B viruses estimated as 93.2%, 2.2% and 4.5%. According to sequencing and phylogenetic analysis HA gene of all A(H1N1)pdm09 viruses belonged to 6B clade (A/South Africa/3626/2013-like), sub-clade 6B1 with substitutions S84N, S162N, I216T located outside of known antigenic sites. Substitution D222G revealed in HA of some H1N1pdm09 sequences from autopsy samples. Whole-genome sequencing of influenza A(H1N1)pdm09 viruses revealed specific mutations in internal genes NEP,NS1,NP,M1 and PA-X common to most of the strains (A. Komissarov et al.,2016). Decrease of population immunity level in pre-epidemic period (October 2015) registered in number of cities of Russia by determination of the GMT of antibiotics and percent of people seropositive to A(H1N1)pdm09 virus.