title: Masking through averages--intraprovincial heterogeneity in HIV prevalence within the Western Cape.
abstract: OBJECTIVE
  To measure HIV prevalence at health-district level in the Western Cape (WC) and to compare these findings with those of the National HIV Antenatal Surveys (NHASs). This investigation aimed to estimate the degree of heterogeneity of HIV prevalence within the province in order to inform the design of appropriate and targeted HIV interventions.
  
  
  METHODS
  Annual cross-sectional, unlinked district HIV antenatal surveys were implemented in all 25 health districts of the WC for the years 2001 - 2004, concurrently with the NHAS. A stratified proportional sample was drawn for each district, involving all 344 antenatal clinics in the province, and the anonymous screening method as described by the World Health Organization (WHO) was applied.
  
  
  RESULTS
  The NHAS revealed a significant increase in HIV prevalence in the WC from 8.6% (95% confidence interval (CI): 5.6 - 11.6) in 2001 to 15.4% (95% CI: 12.5 - 18.2) in 2004. The district-level HIV surveys showed wide variation in HIV prevalence across the health districts, which increased progressively during this period (a range of 0.6 - 22% for the year 2001 increased to 1 - 33% in 2004). Spatial analysis of HIV prevalence by health district for this period also revealed progressive spatial growth of the sub-epidemics, with the highest prevalence observed in districts located in the Cape metropole region.
  
  
  CONCLUSIONS
  These concurrent surveys highlight the fact that examining a provincial estimate of HIV prevalence alone has the potential to mask epicentres within the province. This underscores the importance of expanding the surveillance systems to detect heterogeneity sub-provincially, in order to link with local-level planning and resource allocation.
authors.affiliation: HIV/AIDS Directorate, Department of Health, Western Cape, South Africa. nshaikh@pawc.wcape.gov.za
authors.forename: Najma
authors.initials: N
authors.lastname: Shaikh
authors.forename: Fareed
authors.initials: F
authors.lastname: Abdullah
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Lombard
authors.forename: Lynette
authors.initials: L
authors.lastname: Smit
authors.forename: Debbie
authors.initials: D
authors.lastname: Bradshaw
authors.forename: Lindiwe
authors.initials: L
authors.lastname: Makubalo
mesh_terms: D035041:Anonymous Testing; D002391:Catchment Area, Health / Q000706:statistics & numerical data*; D016000:Cluster Analysis; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D015528:HIV Seroprevalence / Q000639:trends*; D006285:Health Planning / Q000458:organization & administration; D006306:Health Surveys; D006801:Humans; D010865:Pilot Projects; D011159:Population Surveillance / Q000379:methods*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D011296:Prenatal Diagnosis; D012111:Residence Characteristics; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D014504:Urban Health / Q000706:statistics & numerical data