title: Molecular epidemiology of H9N2 influenza viruses in Northern Europe.
abstract: Low pathogenic avian influenza viruses are maintained in wild bird populations throughout the world. Avian influenza viruses are characterized by their efficient ability to reassort and adapt, which enables them to cross the species barrier and enhances their zoonotic potential. Influenza viruses of the H9N2 subtype appear endemic among poultry in Eurasia. They usually exist as low-pathogenic strains and circulate between wild bird populations, poultry and birds sold at live bird markets. Direct transmission of H9N2 viruses, with receptor specificities similar to human influenza strains, to pigs and humans has been reported on several occasions. H9N2 virus was first encountered in Finland in 2009, during routine screening of hunted wild waterfowl. The next year, H9N2 influenza viruses were isolated from wild birds on four occasions, including once from a farmed mallard. We have investigated the relationship between the reared and wild bird isolates by sequencing the hemagglutinin and the neuraminidase genes of the Finnish H9N2 viruses. Nucleotide sequence comparison and phylogenetic analyses indicate that H9N2 was transmitted from wild birds to reared birds in 2010, and that highly identical strains have been circulating in Europe during the last few years.
authors.affiliation: Department of Virology, Haartman Institute, Faculty of Medicine, University of Helsinki, P.O. Box 21, FI-00014 Helsinki, Finland. Electronic address: erika.lindh@helsinki.fi.
authors.forename: Erika
authors.initials: E
authors.lastname: Lindh
authors.affiliation: Research and Laboratory Department, Veterinary Virology, Finnish Food Safety Authority Evira, Mustialankatu 3, FI-00790 Helsinki, Finland. Electronic address: christine.ek-kommonen@evira.fi.
authors.forename: Christine
authors.initials: C
authors.lastname: Ek-Kommonen
authors.affiliation: Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 62, FI-00014 Helsinki, Finland. Electronic address: veli-matti.vaananen@helsinki.fi.
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Väänänen
authors.affiliation: Department of Virology, Haartman Institute, Faculty of Medicine, University of Helsinki, P.O. Box 21, FI-00014 Helsinki, Finland; Department of Virology and Immunology, Helsinki University Central Hospital Laboratory, HUSLAB, P.O. Box 400, FI-00029 Helsinki, Finland. Electronic address: antti.vaheri@helsinki.fi.
authors.forename: Antti
authors.initials: A
authors.lastname: Vaheri
authors.affiliation: Department of Virology, Haartman Institute, Faculty of Medicine, University of Helsinki, P.O. Box 21, FI-00014 Helsinki, Finland; Department of Virology and Immunology, Helsinki University Central Hospital Laboratory, HUSLAB, P.O. Box 400, FI-00029 Helsinki, Finland; Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, P.O. Box 66, FI-00014 Helsinki, Finland. Electronic address: olli.vapalahti@helsinki.fi.
authors.forename: Olli
authors.initials: O
authors.lastname: Vapalahti
authors.affiliation: Research and Laboratory Department, Veterinary Virology, Finnish Food Safety Authority Evira, Mustialankatu 3, FI-00790 Helsinki, Finland. Electronic address: anita.huovilainen@helsinki.fi.
authors.forename: Anita
authors.initials: A
authors.lastname: Huovilainen
mesh_terms: D000818:Animals; D001717:Birds / Q000821:virology*; D004196:Disease Outbreaks / Q000662:veterinary; D005387:Finland / Q000453:epidemiology; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology*; D017720:Molecular Epidemiology; D010802:Phylogeny
keywords: H9N2; Influenza virus; Poultry; Surveillance; Waterfowl