[H1N1V influenza epidemic of 2009 in Russia].

ABSTRACT

The paper describes dynamics, distribution and morbidity rate during the 2009 A(H1N1)v influenza epidemic in Russia. The epidemic appears to have been especially severe in the cities of the Far-East and Siberian Federal Districts where the average morbidity rate ranged from 6.4% to 19.2% (mean 10.3%) and the epidemic duration from 7.8 to 8 weeks. In less affected Southern and Central Federal Districts A(H1N1)v influenza occurred in 5.7% of the population. Schoolchildren aged 7-4 years showed the highest morbidity rate of 28.8%. The age group of 18-53 years accounted for 79.4% of the total lethality. Viral isolates were genetically stable and exhibited 98.9% hemagglutnin (HA) homology with reference viruses. None of the strains had an amino acid substitution at position 275 of neuraminidase (NA) responsible for resistance to oseltamivir. Towards the end of the epidemic, the viral population displayed a significant rise in the number of strains containing mutations in 4 genes (4 HA, 2 NA, 2 PB2 and 1 PA mutations respectively). 26.7% of the viral isolates obtained in the end of the epidemic had D222G substitution responsible for tropism of viruses to lung tissues. Epidemiologically, the 2009 A(H1NI)v influenza epidemic is described as moderate based on the absence of pathogenicity determinants typical of both A(H1N1) influenza virus of 1918 and A(H5N1) virus. The paper compares the 2009 epidemic with those caused by A/Honkong/68 and A/USSR/ 90/77 viruses. The necessity of classification for the discrimination between A(H1N1) subtype viruses is emphasized.