Assessing evidence for avian-to-human transmission of influenza A/H9N2 virus in rural farming communities in northern Vietnam

J Gen Virol. 2017 Aug;98(8):2011-2016. doi: 10.1099/jgv.0.000877. Epub 2017 Aug 4.

Abstract

Rural farming communities in northern Vietnam do not routinely practice vaccination for influenza A viruses (IAV) for either humans or poultry, which enables us to study transmission intensity via seroepidemiology. Using samples from a longitudinal cohort of farming households, we determined the number of symptomatic and asymptomatic human infections for seasonal IAV and avian A/H9 over 2 years. As expected, we detected virologically confirmed acute cases of seasonal IAV in humans, as well as large numbers of subclinical seroconversions to A/H1pdm [55/265 (21 %)], A/H3 [95/265 (36 %)] and A/H9 [24/265 (9 %)]. Five of the A/H9 human seroconverters likely represented true infections rather than heterosubtypic immunity, because the individuals seroconverted solely to A/H9. Among co-located poultry, we found significantly higher seroprevalance for A/H5 compared to A/H9 in both chickens and ducks [for northern study sites overall, 337/1105 (30.5 %) seropositive for A/H5 and 123/1105 (11.1 %) seropositive for A/H9].

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Agriculture
  • Animals
  • Antibodies, Viral / blood
  • Chickens
  • Child
  • Child, Preschool
  • Ducks
  • Female
  • Humans
  • Infant
  • Influenza A Virus, H9N2 Subtype / classification
  • Influenza A Virus, H9N2 Subtype / genetics
  • Influenza A Virus, H9N2 Subtype / immunology
  • Influenza A Virus, H9N2 Subtype / isolation & purification*
  • Influenza in Birds / blood
  • Influenza in Birds / epidemiology
  • Influenza in Birds / transmission
  • Influenza in Birds / virology*
  • Influenza, Human / blood
  • Influenza, Human / epidemiology
  • Influenza, Human / transmission
  • Influenza, Human / virology*
  • Male
  • Middle Aged
  • Poultry Diseases / blood
  • Poultry Diseases / epidemiology
  • Poultry Diseases / transmission
  • Poultry Diseases / virology*
  • Rural Population / statistics & numerical data
  • Seroepidemiologic Studies
  • Vietnam
  • Young Adult

Substances

  • Antibodies, Viral