Molecular mechanisms of infection and pathogenesis of viruses

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Influenza A viruses of different subtypes were isolated from fecal samples of ducks in their nesting areas in Siberia. Phylogenetic analysis of the NP genes of the isolates in Siberia and those in Hokkaido, Japan on their flyway of migration from Siberia to the south in autumn revealed that they belong to the Eurasian lineage of avian influenza viruses. It is noted that the genes of the isolates in Siberia are closely related to those of H5N1 influenza virus strains isolated from chickens and humans in Hong Kong in 1997 as well as to those of isolates from domestic birds in southern China. The results indicate that influenza viruses perpetuated in ducks nesting in Siberia should have contributed genes in the emergence of the H5N1 virus in Hong Kong.Vaccine prepared from avirulent A/ duck/ Hokkaido/ 4/ 96 (H5N3) influenza virus was potent enough to protect mice from challenge with leathal dose of the pathogenic H5N1 virus. Intensive surveillance study of aquatic birds especially in Siberia is, therefore, stressed to provide information on the future pandemic influenza virus strains and for vaccine preparation.Serological surveillance revealed that H5 influenza virus infections had occurred in pigs in southern China since at least 1977. It is also shown that H9 viruses have circulated among them after 1983.