title: Transmission dynamics of pandemic influenza A(H1N1)pdm09 virus in humans and swine in backyard farms in Tumbes, Peru.
abstract: OBJECTIVE
  We aimed to determine the frequency of pH1N1 transmission between humans and swine on backyard farms in Tumbes, Peru.
  
  
  METHODS
  Two-year serial cross-sectional study comprising four sampling periods: March 2009 (pre-pandemic), October 2009 (peak of the pandemic in Peru), April 2010 (1st post-pandemic period), and October 2011 (2nd post-pandemic period).
  
  
  METHODS
  Backyard swine serum, tracheal swabs, and lung sample were collected during each sampling period.
  
  
  METHODS
  We assessed current and past pH1N1 infection in swine through serological testing, virus culture, and RT-PCR and compared the results with human incidence data from a population-based active surveillance cohort study in Peru.
  
  
  RESULTS
  Among 1303 swine sampled, the antibody prevalence to pH1N1 was 0% pre-pandemic, 8% at the peak of the human pandemic (October 2009), and 24% in April 2010 and 1% in October 2011 (post-pandemic sampling periods). Trends in swine seropositivity paralleled those seen in humans in Tumbes. The pH1N1 virus was isolated from three pigs during the peak of the pandemic. Phylogenetic analysis revealed that these viruses likely represent two separate human-to-swine transmission events in backyard farm settings.
  
  
  CONCLUSIONS
  Our findings suggest that human-to-swine pH1N1 transmission occurred during the pandemic among backyard farms in Peru, emphasizing the importance of interspecies transmission in backyard pig populations. Continued surveillance for influenza viruses in backyard farms is warranted.
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.|Johns Hopkins School of Public Health, Baltimore, MD, USA.
authors.forename: Yeny O
authors.initials: YO
authors.lastname: Tinoco
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.|U.S. Centers for Disease Control and Prevention, Division of Global Health Protection, Nairobi, Kenya.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Montgomery
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.
authors.forename: Mathew R
authors.initials: MR
authors.lastname: Kasper
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Martha I
authors.initials: MI
authors.lastname: Nelson
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.
authors.forename: Hugo
authors.initials: H
authors.lastname: Razuri
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Guezala
authors.affiliation: U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Azziz-Baumgartner
authors.affiliation: U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Marc-Alain
authors.initials: MA
authors.lastname: Widdowson
authors.affiliation: U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Barnes
authors.affiliation: Johns Hopkins School of Public Health, Baltimore, MD, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.affiliation: U.S. Naval Medical Research Unit No. 6, Lima, Peru.|Tulane School of Public Health and Tropical Medicine, New Orleans, LA, USA.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Bausch
authors.affiliation: San Marcos University, Veterinary School, Lima, Peru.
authors.forename: Armando E
authors.initials: AE
authors.lastname: Gonzalez
mesh_terms: D000818:Animals; D018562:Disease Transmission, Infectious / Q000662:veterinary*; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000502:physiology*; D007251:Influenza, Human / Q000635:transmission*; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary*; D010568:Peru; D010802:Phylogeny; D034421:Sus scrofa; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000635:transmission*
keywords: Antibodies; backyard pig farms; human-animal transmission; influenza