title: Mapping the global distribution of trachoma.
abstract: OBJECTIVE
  We aimed to summarize and map the existing global population-based data on active trachoma and trichiasis. Detailed distribution maps of various infectious diseases have proved a valuable tool in their control. Such maps play an important role in assessing the magnitude of the problem, defining priority areas for control, monitoring changes, and advocacy. Until now, information on trachoma prevalence at within country levels has not been systematically collated, analysed and reported.
  
  
  METHODS
  We gathered the last 18 years' worth of reported data on active trachoma in children aged less than 10 years, and the last 25 years of reported trichiasis in adults aged 15 years and over from 139 population-based surveys in 33 countries. We collated these data into one database using the "district" (second administrative level) as the standard unit of reporting. We used Geographical Information Systems as a database and cartographic tool to generate a global map of the prevalence of trachoma and trichiasis.
  
  
  RESULTS
  We obtained data on active trachoma and trichiasis from 18 countries in the WHO African Region, 6 in the Eastern Mediterranean Region, 3 in the South-East Asia Region, 3 in the Western Pacific Region and 2 in the Region of the Americas. In 23 countries suspected of having endemic trachoma no reliable district-level population-based data were available. In China and India, data were limited to a few districts. The data highlighted important regional differences and marked national variations in prevalence of active trachoma and trichiasis.
  
  
  CONCLUSIONS
  This is the first attempt to summarize and map the existing population-based data on active trachoma and trichiasis. The lack of data in many countries remains an important obstacle to trachoma control efforts.
authors.affiliation: Clinical Research Unit, London School of Hygiene and Tropical Medicine, London, England. sarah.polack@1shtm.ac.uk
authors.forename: Sarah
authors.initials: S
authors.lastname: Polack
authors.forename: Simon
authors.initials: S
authors.lastname: Brooker
authors.forename: Hannah
authors.initials: H
authors.lastname: Kuper
authors.forename: Silvio
authors.initials: S
authors.lastname: Mariotti
authors.forename: David
authors.initials: D
authors.lastname: Mabey
authors.forename: Allen
authors.initials: A
authors.lastname: Foster
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001766:Blindness / Q000453:epidemiology* / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D002980:Climate; D016000:Cluster Analysis; D004781:Environmental Exposure; D005141:Eyelid Diseases / Q000453:epidemiology* / Q000382:microbiology; D040362:Geographic Information Systems; D005843:Geography; D014943:Global Health; D006297:Health Services Accessibility; D006801:Humans; D007223:Infant; D008377:Maps as Topic; D008875:Middle Aged; D015995:Prevalence; D040442:Public Health Informatics; D012307:Risk Factors; D014141:Trachoma / Q000150:complications / Q000453:epidemiology*