title: New avian influenza A virus subtype combination H5N7 identified in Danish mallard ducks.
abstract: During the past years increasing incidences of influenza A zoonosis have made it of uppermost importance to possess methods for rapid and precise identification and characterisation of influenza A viruses. We present here a convenient one-step RT-PCR method that will amplify full-length haemagglutinin (HA) and neuraminidase (NA) directly from clinical samples and from all known subtypes of influenza A. We applied the method on samples collected in September 2003 from a Danish flock of mallards with general health problems and by this a previously undescribed influenza A subtype combination, H5N7, was identified. The HA gene showed great sequence similarity to the highly pathogenic avian influenza A virus (HPAIV) A/Chicken/Italy/312/97 (H5N2); however, the cleavage site sequence between HA1 and HA2 had a motif typical for low pathogenic avian influenza viruses (LPAIV). The full-length NA sequence was most closely related to the HPAIV A/Chicken/Netherlands/01/03 (H7N7) that infected chickens and humans in the Netherlands in 2003. Ten persons with direct or indirect contact with the Danish mallard ducks showed signs of influenza-like illness 2-3 days following the killing of the ducks, but no evidence of influence infections was detected. To our knowledge this is the first report of an H5N7 influenza A virus.
authors.affiliation: Department of Virology, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Bragstad
authors.forename: P H
authors.initials: PH
authors.lastname: Jørgensen
authors.forename: K J
authors.initials: KJ
authors.lastname: Handberg
authors.forename: S
authors.initials: S
authors.lastname: Mellergaard
authors.forename: S
authors.initials: S
authors.lastname: Corbet
authors.forename: A
authors.initials: A
authors.lastname: Fomsgaard
mesh_terms: D000818:Animals; D018076:DNA, Complementary; D004279:DNA, Viral / Q000737:chemistry / Q000378:metabolism; D003718:Denmark; D004372:Ducks / Q000821:virology; D005814:Genes, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D009980:Influenza A virus / Q000145:classification* / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000821:virology*; D007251:Influenza, Human / Q000821:virology*; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D012367:RNA, Viral / Q000032:analysis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014764:Viral Proteins / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D004279:DNA, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D014764:Viral Proteins; D009439:Neuraminidase