1. Scenarios for Future Demand for ART Methods and Assumptions
UNAIDS/WHO Working Group

2. Overview HIV prevalence projections Estimating numbers needing ART
Scenario assumptions for scale up

3. Classification of HIV Epidemics
Low-level: no identifiable group has prevalence >5%
Concentrated: “transmission not sustained outside core groups”: prevalence among pregnant women below 1% in urban areas, but some groups at high risk have prevalence >5%
Generalised: “transmission sustained outside core groups”: prevalence among pregnant women consistently over 1%

4. HIV Prevalence Projections
Generalized epidemics: HIV prevalence trend based on ANC surveillance, assumed stable epidemics into the future
Concentrated and Low-level epidemics:
Estimated size of groups at risk
Estimated current prevalence based on recent surveillance data
Projections based on assumptions of HIV prevalence saturations in high-risk groups

5. Number newly needing ART
The number newly needing ART in each year is assumed to be the number of people who would die within 2 years without ART
Proxy for the WHO guideline – CD4 count below 200
This will depend on the incidence of HIV some years previously (corresponding to the time of infection)
From , this is mostly determined by HIV incidence that has already taken place

6. Total number needing ART
Total number needing ART = Number newly needing + Number of survivors from the previous year (including those receiving ART)
The number receiving ART therefore accumulates in future years
Need in future years depends on the number receiving treatment in previous years
Scenarios are dominated by scale up assumptions

7. Low Scenario Assumptions
Baseline coverage was calculated for each country from the most recent ‘3 by 5’ report
Percentage of those in need who actually receive ART
Coverage is then assumed to increase in a linear way in every country, to reach a level of 60% in the year 2012.
Scale up is therefore faster in countries with a lower starting point

8. High Scenario Assumptions
The baseline is the unmet need, and the rate at which it decreases, as observed in the most recent ‘3 by 5’ reports
The percentage of unmet need is assumed to decrease in a linear way in every country until coverage reaches 85%
Uses observed rates of decrease of the most urgent unmet need (1 yr from death) from previous years, by country
Coverage increases in a non-linear way
Scale up assumes steadily increasing coverage for new cases