title: Measuring the impact of the global response to the AIDS epidemic: challenges and future directions.
abstract: OBJECTIVE
  In the Declaration of Commitment of the 2001 United Nations General Assembly Special Session on AIDS, all Member States agreed to a series of actions to address HIV. This article examines the availability of data to measure progress toward reducing HIV incidence and AIDS mortality and discusses the extent to which changes can be attributed to programs.
  
  
  METHODS
  Lacking a method to directly measure HIV incidence, trends in HIV prevalence among 15-year to 24-year olds and groups with high-risk behaviors are used as a proxy measure for incidence trends among adults in generalized and concentrated/low-level epidemics, respectively. Although there is limited empirical data on trends in new infections among children, progress in the treatment area is tracked through indicators for the percentage of people who remain on antiretroviral treatment 12 months after initiation and the coverage of antiretroviral treatment. Successive iterations of epidemiological models using surveillance data from pregnant women and groups with high-risk behavior and data from national household surveys, demographic data and epidemiological assumptions have produced increasingly robust estimates of HIV prevalence, incidence and mortality.
  
  
  RESULTS
  Globally, incidence has decreased among adults (accompanied by evidence of changes in behavior in several countries) and children over the past decade. The decline in AIDS mortality is more recent. On the basis of the underlying logical framework and mathematical models, it is concluded that programs have contributed to a reduction in HIV incidence and AIDS mortality.
  
  
  CONCLUSIONS
  More data are needed to reliably inform trends in HIV incidence and AIDS mortality in many countries to allow an assessment of progress against national and global targets. In addition, impact evaluation studies are needed to assess the relationship between changes in incidence and mortality and the HIV response and to determine the extent to which these changes can be attributed to specific programmatic interventions.
authors.affiliation: UNAIDS, Geneva, Switzerland.
authors.forename: Mary
authors.initials: M
authors.lastname: Mahy
authors.forename: Matthew
authors.initials: M
authors.lastname: Warner-Smith
authors.forename: Karen A
authors.initials: KA
authors.lastname: Stanecki
authors.forename: Peter D
authors.initials: PD
authors.lastname: Ghys
mesh_terms: D000328:Adult; D014943:Global Health; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control; D008962:Models, Theoretical; D009313:National Health Programs; D014480:United Nations