title: Animal influenza epidemiology.
abstract: Influenza A viruses exist within their natural host, aquatic birds, in a number of antigenic subtypes. Only a few of these subtypes have successfully crossed into other avian and mammalian hosts. This brief review will focus on just three examples of viruses that have successfully passed between species; avian H5NI1 and H9N2 viruses and H3N2 viruses which have transmitted from aquatic birds to humans and then to swine. Although there are a number of other subtypes that have also transmitted successfully between species, these three selected examples have spread and evolved in different ways, exemplifying the complexity of influenza A virus epidemiology.
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Ducatez
authors.forename: R G
authors.initials: RG
authors.lastname: Webster
authors.forename: R J
authors.initials: RJ
authors.lastname: Webby
mesh_terms: D000818:Animals; D001717:Birds; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D053124:Influenza A Virus, H5N1 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D053127:Influenza A Virus, H9N2 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D005585:Influenza in Birds / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D007251:Influenza, Human / Q000821:virology*; D009976:Orthomyxoviridae Infections / Q000662:veterinary*; D013552:Swine