The Asian Epidemic Model: a process model for exploring HIV policy and programme alternatives in Asia.

Process models offer opportunities to explore the effectiveness of different programme and policy alternatives by varying input behaviours and model parameters to reflect programmatic/policy effects. The Asian Epidemic Model (AEM) has been designed to reflect the primary groups and transmission modes driving HIV transmission in Asia. The user adjusts AEM fitting parameters until HIV prevalence outputs from the model agree with observed epidemiological trends. The AEM resultant projections are closely tied to the epidemiological and behavioural data in the country. In Thailand and Cambodia they have shown good agreement with observed epidemiological trends in surveillance populations and with changes in HIV transmission modes, AIDS cases, male:female ratios over time, and other external validation checks. By varying the input behaviours and STI trends, one can examine the impact of different prevention efforts on the future course of the epidemic. In conclusion, the AEM is a semi-empirical model, which has worked well in Asian settings. It provides a useful tool for policy and programme analysis in Asian countries.