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Projecting the demographic impact of AIDS and the number of people in need of treatment: updates to the Spectrum projection package
  1. J Stover1,
  2. N Walker2,
  3. N C Grassly3,
  4. M Marston4
  1. 1Futures Group, Glastonbury, CT, USA
  2. 2UNICEF, New York, NY, USA
  3. 3Imperial College, London, UK
  4. 4London School of Hygiene and Tropical Medicine, London, UK
  1. Correspondence to:
 MrJ Stover
 Futures Group, 80 Glastonbury Boulevard, Glastonbury, CT 06033, USA; JStover{at}


Background: In the Joint United Nations Programme on HIV/AIDS (UNAIDS) approach to HIV and AIDS estimates, estimates of adult prevalence produced by the Estimation and Projection Package (EPP) or the Workbook are transferred to Spectrum to estimate the consequences of the HIV/AIDS epidemic, including the number of people living with HIV by age and sex, new infections, AIDS deaths, AIDS orphans, treatment needs, and the impact of treatment on survival.

Methods: The UNAIDS Reference Group on Estimates, Models and Projections recommends updates to the methodology and assumptions based on the latest research findings and international policy and programme guidelines. The latest update to Spectrum has been used in the 2005 round of global estimates.

Results: Several new features have been added to Spectrum in the past two years. New patterns of the age distribution of prevalence over time are based on the latest survey data. A more detailed treatment of mother to child transmission of HIV is now based on information about current breastfeeding practices, treatment options offered to prevent mother to child transmission (PMTCT), infant feeding options, and the percentage or number of pregnant women accessing PMTCT services. A new section on child survival includes the effects of cotrimoxazole and ART on child survival. Projections can now be calibrated with national survey data. A new set of outputs is provided for all adults over the age of 15 in addition to the traditional 15–49 age group. New outputs are now available to show plausibility bounds and regional estimates for key indicators.

Conclusions: The latest update to the Spectrum program is intended to incorporate the latest research findings and provide new outputs needed by national and international planners.

  • EPP, Estimation and Projection Package
  • FHI, Family Health International
  • PMTCT, prevention of mother to child transmission
  • PSI, Population Services International
  • UNAIDS, Joint United Nations Programme on HIV/AIDS
  • HIV
  • modelling
  • AIDS
  • estimates

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  • Competing interests: none.

  • Edited by Peter Ghys, Neff Walker, Helen Ward and Rob Miller