Sources of Infections and National Intervention Impact Projections
To help optimize the allocation of resources in HIV prevention programmes, the UNAIDS/World Bank initiative ‘Know Your Epidemic – Know Your Response’ has been designed to facilitate programme managers to examine the sources of HIV infections in a country, which can then be used to guide prevention programme and data collection priorities. The method for estimating sources of infection is the ‘Modes of Transmission’ model, a spreadsheetbased tool that uses inputs on the numbers of individuals in particular risk groups (sex workers, clients of sex workers, those with casual partnerships, etc.), HIV prevalence and behaviours among the groups and transmission risk associated with the behaviours to project the number of new infections in each group in the next year. This model been applied in several countries but questions have been raised about the accuracy of results. The HIV Modelling Consortium convened a meeting of expert epidemiologists, demographers, mathematical modellers and programme implemeneters to review methods for estimating sources of HIV infections. A secondary aim was to understand how the assumptions other models make about the sources of HIV infection in populations influences the projections they make about the impact of different interventions.