title: Characterization of a newly emerged genetic cluster of H1N1  and H1N2 swine influenza virus in the United States.
abstract: H1 influenza A viruses that were distinct from the classical swine H1 lineage were identified in pigs in Canada in 2003–2004; antigenic and genetic characterization identified the hemagglutinin (HA) as human H1 lineage. The viruses identified in Canadian pigs were human lineage in entirety or double (human–swine) reassortants. Here, we report the whole genome sequence analysis of four human-like H1 viruses isolated from U.S. swine in 2005 and 2007. All four isolates were characterized as triple reassortants with an internal gene constellation similar to contemporary U.S. swine influenza virus (SIV), with HA and neuraminidase (NA) most similar to human influenza virus lineages. A 2007 human-like H1N1 was evaluated in a pathogenesis and transmission model and compared to a 2004 reassortant H1N1 SIV isolate with swine lineage HA and NA. The 2007 isolate induced disease typical of influenza virus and was transmitted to contact pigs; however, the kinetics and magnitude differed from the 2004 H1N1 SIV. This study indicates that the human-like H1 SIV can efficiently replicate and transmit in the swine host and now co-circulates with contemporary SIVs as a distinct genetic cluster of H1 SIV.
authors: Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA-ARS, 2300 Dayton Road, Ames, IA 50010, USA. amy.vincent@ars.usda.gov
authors: Amy L
authors: AL
authors: Vincent
authors: Wenjun
authors: W
authors: Ma
authors: Kelly M
authors: KM
authors: Lager
authors: Marie R
authors: MR
authors: Gramer
authors: Juergen A
authors: JA
authors: Richt
authors: Bruce H
authors: BH
authors: Janke
mesh_terms: D000818:Animals; D016679:Genome, Viral; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D057221:Influenza A Virus, H1N2 Subtype / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013552:Swine / Q000821:virology*; D013553:Swine Diseases / Q000821:virology*; D014481:United States
chemical_list: D012367:RNA, Viral