The influenza epidemic in Russia in 2014-2015 season
The goal of this study was to compare the data on the intensity of the influenza A(H3N2) and B epidemic (especially the death toll) in 2014-2015 season with the previous epidemic of 2013-2014. The data on weekly morbidity, hospitalization, deaths from influenza and acute respiratory diseases in different age groups of inhabitants of 59 cities located in 7 Federal districts of the Russian Federation were collected using the database of the Research Institute of Influenza. Analysis of this data showed, that the influenza epidemic in 2014-2015 began earlier (in December), compared with the epidemic of 2013-2014, and spread mainly from Europe through Russia to the East. The intensity of the epidemic 2014-2015 was higher, compared to the previous one. The epidemic was more prevalent by regions and cities and wider engagement of different age groups (except children up to 2 years) was observed. At the peak of the epidemic the morbidity level was higher, the average duration of the epidemic was longer and the number of patients among cities inhabitants (especially among children 7-14 years of age and adults) was higher than in the previous season. The rates of hospitalization with influenza and ARI among patients older than 65 years were also higher (1.4 times) as well as frequency of hospitalization with a diagnosis of ‘influenza’ (2.7 times) and the number of deaths from laboratory confirmed influenza (1.8 times). Although the pandemic influenza virus A(H1N1)pdm09, was not the main causative agent of the epidemic 2015, it still was the main cause of deaths from influenza (45.5% of all cases). In spite of influenza A(H1N1)pdm09 virus sporadic prevalence, deaths from it were reported only on the European part of territory of Russia.