Isolation and molecular characterization of the influenza A/H5N1 viruses isolated during the outbreaks of avian influenza among birds in the European part of Russia in 2005: a virus strain with ozeltamivir-resistance mutation was found

The isolation and characterization of the influenza A/H5NI viruses isolated from hens that died during the outbreak of avian influenza in autumn 2005 in the Yandovka village (Tula oblast) and from a wild swan that died near the orifice of the Volga River in the zone of the Karalat Furrow were carried out. Molecular-biologic and phylogenetic analyses were performed with a view of determining possible geographical origin of strains, phylogenetic similarity of viruses and also estimating their pathogenicity, epidemic danger for people, and possible resistance to antiviral drugs. It was shown that the virus belonged to the high pathogenic variants that arose in China as a result of the reassortment of the viruses of the genotypes Z and V that circulated among poultry and wild birds. A number of molecular markers characterizing the high pathogenicity of the virus for gallinaceous birds and mammals were revealed, but the specific mutations in the hemagglutinin gene that promote the high rate of virus replication in a human organism and also the mutations of adaptation to it were not found. It was shown that the variants of the influenza A/H5N1 virus that circulated in this epizootic were sensitive to remantadine. The strain isolated from the wild swan had the mutation causing resistance to Tamiflu/ozeltamivir.