title: Reverse zoonosis of influenza to swine: new perspectives on the human-animal interface.
abstract: The origins of the 2009 influenza A (H1N1) pandemic in swine are unknown, highlighting gaps in our understanding of influenza A virus (IAV) ecology and evolution. We review how recently strengthened influenza virus surveillance in pigs has revealed that influenza virus transmission from humans to swine is far more frequent than swine-to-human zoonosis, and is central in seeding swine globally with new viral diversity. The scale of global human-to-swine transmission represents the largest 'reverse zoonosis' of a pathogen documented to date. Overcoming the bias towards perceiving swine as sources of human viruses, rather than recipients, is key to understanding how the bidirectional nature of the human-animal interface produces influenza threats to both hosts.
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: nelsonma@mail.nih.gov.
authors.forename: Martha I
authors.initials: MI
authors.lastname: Nelson
authors.affiliation: Virus and Prion Research Unit, National Animal Disease Center, US Department of Agriculture (USDA) Agricultural Research Service (ARS), Ames, IA 50010, USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Vincent
mesh_terms: D000818:Animals; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity; D009980:Influenza A virus / Q000235:genetics / Q000472:pathogenicity; D007251:Influenza, Human / Q000635:transmission* / Q000821:virology; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000635:transmission* / Q000821:virology; D015047:Zoonoses
keywords: evolution; human–animal interface; influenza A virus; pandemic; swine