title: Estimating household and community transmission of ocular Chlamydia trachomatis.
abstract: BACKGROUND
  Community-wide administration of antibiotics is one arm of a four-pronged strategy in the global initiative to eliminate blindness due to trachoma. The potential impact of more efficient, targeted treatment of infected households depends on the relative contribution of community and household transmission of infection, which have not previously been estimated.
  
  
  METHODS
  A mathematical model of the household transmission of ocular Chlamydia trachomatis was fit to detailed demographic and prevalence data from four endemic populations in The Gambia and Tanzania. Maximum likelihood estimates of the household and community transmission coefficients were obtained.
  
  
  RESULTS
  The estimated household transmission coefficient exceeded both the community transmission coefficient and the rate of clearance of infection by individuals in three of the four populations, allowing persistent transmission of infection within households. In all populations, individuals in larger households contributed more to the incidence of infection than those in smaller households.
  
  
  CONCLUSIONS
  Transmission of ocular C. trachomatis infection within households is typically very efficient. Failure to treat all infected members of a household during mass administration of antibiotics is likely to result in rapid re-infection of that household, followed by more gradual spread across the community. The feasibility and effectiveness of household targeted strategies should be explored.
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, UK. isobel.blake02@imperial.ac.uk
authors.forename: Isobel M
authors.initials: IM
authors.lastname: Blake
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Burton
authors.forename: Robin L
authors.initials: RL
authors.lastname: Bailey
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Solomon
authors.forename: Sheila
authors.initials: S
authors.lastname: West
authors.forename: Beatriz
authors.initials: B
authors.lastname: Muñoz
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Holland
authors.forename: David C W
authors.initials: DC
authors.lastname: Mabey
authors.forename: Manoj
authors.initials: M
authors.lastname: Gambhir
authors.forename: María-Gloria
authors.initials: MG
authors.lastname: Basáñez
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Grassly