title: Influenza A Viruses of Human Origin in Swine, Brazil.
abstract: The evolutionary origins of the influenza A(H1N1)pdm09 virus that caused the first outbreak of the 2009 pandemic in Mexico remain unclear, highlighting the lack of swine surveillance in Latin American countries. Although Brazil has one of the largest swine populations in the world, influenza was not thought to be endemic in Brazil's swine until the major outbreaks of influenza A(H1N1)pdm09 in 2009. Through phylogenetic analysis of whole-genome sequences of influenza viruses of the H1N1, H1N2, and H3N2 subtypes collected in swine in Brazil during 2009-2012, we identified multiple previously uncharacterized influenza viruses of human seasonal H1N2 and H3N2 virus origin that have circulated undetected in swine for more than a decade. Viral diversity has further increased in Brazil through reassortment between co-circulating viruses, including A(H1N1)pdm09. The circulation of multiple divergent hemagglutinin lineages challenges the design of effective cross-protective vaccines and highlights the need for additional surveillance.
authors.forename: Martha I
authors.initials: MI
authors.lastname: Nelson
authors.forename: Rejane
authors.initials: R
authors.lastname: Schaefer
authors.forename: Danielle
authors.initials: D
authors.lastname: Gava
authors.forename: Maurício Egídio
authors.initials: ME
authors.lastname: Cantão
authors.forename: Janice Reis
authors.initials: JR
authors.lastname: Ciacci-Zanella
mesh_terms: D000818:Animals; D001938:Brazil / Q000453:epidemiology; D018562:Disease Transmission, Infectious; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D009980:Influenza A virus / Q000235:genetics*; D007251:Influenza, Human / Q000453:epidemiology*; D010802:Phylogeny; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology*
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus
keywords: Brazil; evolution; humans; influenza; influenza A virus; interspecies transmission; pigs; reassortment; swine; viruses; zoonoses