title: Recombination resulting in virulence shift in avian influenza outbreak, Chile.
abstract: Influenza A viruses occur worldwide in wild birds and are occasionally associated with outbreaks in commercial chickens and turkeys. However, avian influenza viruses have not been isolated from wild birds or poultry in South America. A recent outbreak in chickens of H7N3 low pathogenic avian influenza (LPAI) occurred in Chile. One month later, after a sudden increase in deaths, H7N3 highly pathogenic avian influenza (HPAI) virus was isolated. Sequence analysis of all eight genes of the LPAI virus and the HPAI viruses showed minor differences between the viruses except at the hemagglutinin (HA) cleavage site. The LPAI virus had a cleavage site similar to other low pathogenic H7 viruses, but the HPAI isolates had a 30-nucleotide insert. The insertion likely occurred by recombination between the HA and nucleoprotein genes of the LPAI virus, resulting in a virulence shift. Sequence comparison of all eight gene segments showed the Chilean viruses were also distinct from all other avian influenza viruses and represent a distinct South American clade.
authors.affiliation: Southeast Poultry Research Laboratory, Athens, Georgia, USA. dsuarez@seprl.usda.gov
authors.forename: David L
authors.initials: DL
authors.lastname: Suarez
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Senne
authors.forename: Jill
authors.initials: J
authors.lastname: Banks
authors.forename: Ian H
authors.initials: IH
authors.lastname: Brown
authors.forename: Steve C
authors.initials: SC
authors.lastname: Essen
authors.forename: Chang-Won
authors.initials: CW
authors.lastname: Lee
authors.forename: Ruth J
authors.initials: RJ
authors.lastname: Manvell
authors.forename: Christian
authors.initials: C
authors.lastname: Mathieu-Benson
authors.forename: Valentina
authors.initials: V
authors.lastname: Moreno
authors.forename: Janice C
authors.initials: JC
authors.lastname: Pedersen
authors.forename: Brundaban
authors.initials: B
authors.lastname: Panigrahy
authors.forename: Hernán
authors.initials: H
authors.lastname: Rojas
authors.forename: Erica
authors.initials: E
authors.lastname: Spackman
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Alexander
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001717:Birds; D002677:Chile / Q000453:epidemiology; D004196:Disease Outbreaks; D009980:Influenza A virus / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D005585:Influenza in Birds / Q000453:epidemiology* / Q000821:virology; D008969:Molecular Sequence Data; D010802:Phylogeny; D011995:Recombination, Genetic; D014774:Virulence