title: Genetic evolution of swine influenza A (H3N2) viruses in China from 1970 to 2006.
abstract: Pigs are susceptible to both human and avian influenza viruses and have been proposed to be intermediate hosts, or mixing vessels, for the generation of pandemic influenza viruses through reassortment or adaptation to the mammalian host. In this study, we summarize and report for the first time the coexistence of wholly human-like H3N2 viruses, double-reassortant H3N2 viruses, and triple-reassortant H3N2 viruses in pigs in China by analyzing the eight genes of swine influenza A (H3N2) viruses found in China from 1970 to 2006. In 1970, the first wholly human-like H3N2 (Hong Kong/68-like) viruses were isolated from pigs in Taiwan, and then in the next years Victoria/75-like, Sydney/97-like, New York/99-like, and Moscow/99-like swine H3N2 viruses were regularly isolated in China. In the 1980s, two triple-reassortant viruses were isolated from pigs. Recently, the double-reassortant viruses containing genes from the human (HA and NA) and avian (PB2, PB1, PA, NP, M, and NS) lineages and the triple-reassortant viruses containing genes from the human (HA and NA), classical swine (NP), and avian (PB2, PB1, PA, M, and NS) lineages emerged in pigs in China. The coexistence of wholly human-like and reassortant viruses provides further evidence that pigs serve as intermediate hosts, or mixing vessels, and emphasizes the importance of reinforcing swine influenza virus surveillance in China.
authors.affiliation: National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Harbin 150001, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Yu
authors.forename: Rong-Hong
authors.initials: RH
authors.lastname: Hua
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Tian-Qiang
authors.initials: TQ
authors.lastname: Liu
authors.forename: Hui-Li
authors.initials: HL
authors.lastname: Liu
authors.forename: Guo-Xin
authors.initials: GX
authors.lastname: Li
authors.forename: Guang-Zhi
authors.initials: GZ
authors.lastname: Tong
mesh_terms: D000818:Animals; D002681:China; D019143:Evolution, Molecular; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D009976:Orthomyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D016865:Reassortant Viruses / Q000235:genetics; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase