Flu morbidity in January-March, 2016, in Russian Federation. Epidemic and pandemic potential of A / H1N1pdm09 influenza virus

Abstract

The World Health Organization (WHO) searches influenza virus circulation in community and in natural biocenosis, studies virus strains and their properties, develops diagnostic methods and preventive measures since 1940 th worldwide because of epidemic actuality and high pandemic potential of the influenza virus. The Federal Influenza Center (including Federal Research Institute of Influenza, Saint-Petersburg, and the Center of Virus Ecology, D.I.Ivanovskiy Virology Institute, Honorary Academician N.F.Gamaleya Federal Research Center of Epidemiology and Microbiology, Federal Research Center for Epidemiology and Microbiology, Moscow) performs similar work in Russia in close cooperation with WHO within the framework of the International Programme of Influenza Monitoring. A(H1N1)pdm09 influenza virus dominated in the Northern Hemisphere in the 2015 – 2016 epidemic season. Morbidity growth was noted from the end of January, 2016, to the beginning of March, 2016. The peak morbidity at the 5th week of the year exceeded the epidemic threshold (132 cases per 10,000 of population) and morbidity in the 2014 – 2015 season significantly and approached to the peak morbidity of the 2009 – 2010 epidemic season. The epidemic growth in Russian Federation was provided by three influenza viruses: A(H1N1)pdm09, В and A (H3N2). A(H1N1)pdm09 virus caused 18% of all acute respiratory diseases and accounted for 84% of circulating influenza viruses. Flu was diagnosed in patients of different age with maximal frequency in 3- to 6-year old children. Peak admission number was registered at 5 and 6 weeks (3,538 and 4,109 cases, respectively); this number exceeded the similar parameter of the 2009 – 2010 season. Patients of 15 to 64 years old were admitted more often including those with acute respiratory infection. Two hundred and thirty nine deaths were registered to the 5 th of April, 2016, according to data from the Federal Influenza Center and the Center of Virus Ecology. The diagnosis of A(H1N1)pdm09 flu was confirmed in 97.9% of deaths. Molecular analysis of isolated strains of A(H1N1)pdm09 influenza virus revealed amino acid substitutions in receptor binding site and SA site of hemagglutinin and in genes coding intrinsic proteins PA, NP, M1, and NS1. Influenza virus strains resistive to anti-neuraminidase drugs were encountered in #< 1% in the Northern Hemisphere countries. No strains studied were sensitive to adamantine derivates.