PLoS ONE (Jan 2012)

Secondary household transmission of 2009 pandemic influenza A (H1N1) virus among an urban and rural population in Kenya, 2009-2010.

  • Clara Y Kim,
  • Robert F Breiman,
  • Leonard Cosmas,
  • Allan Audi,
  • Barrack Aura,
  • Godfrey Bigogo,
  • Henry Njuguna,
  • Emmaculate Lebo,
  • Lilian Waiboci,
  • M Kariuki Njenga,
  • Daniel R Feikin,
  • Mark A Katz

DOI
https://doi.org/10.1371/journal.pone.0038166
Journal volume & issue
Vol. 7, no. 6
p. e38166

Abstract

Read online

BackgroundIn Kenya, >1,200 laboratory-confirmed 2009 pandemic influenza A (H1N1) (pH1N1) cases occurred since June 2009. We used population-based infectious disease surveillance (PBIDS) data to assess household transmission of pH1N1 in urban Nairobi (Kibera) and rural Lwak.MethodsWe defined a pH1N1 patient as laboratory-confirmed pH1N1 infection among PBIDS participants during August 1, 2009-February 5, 2010, in Kibera, or August 1, 2009-January 20, 2010, in Lwak, and a case household as a household with a laboratory-confirmed pH1N1 patient. Community interviewers visited PBIDS-participating households to inquire about illnesses among household members. We randomly selected 4 comparison households per case household matched by number of children aged ResultsAmong household contacts of patients with confirmed pH1N1 in Kibera, 4.6% had ILI compared with 8.2% in Lwak (risk ratio [RR], 0.5; 95% confidence interval [CI], 0.3-0.9). Household contacts of patients were more likely to have ILIs than comparison-household members in both Kibera (RR, 1.8; 95% CI, 1.1-2.8) and Lwak (RR, 2.6; 95% CI, 1.6-4.3). Overall, ILI was not associated with patient age. However, ILI rates among household contacts were higher among children aged ConclusionsSubstantial pH1N1 household transmission occurred in urban and rural Kenya. Household transmission rates were higher in the rural area.