Calculating the consequences: HAART and risky sex.

Abstract

Since the widespread availability of highly active antiretroviral therapy (HAART) in 1996, many have wondered what effect the widespread usage of these therapies will have on the incidence of HIV. In an extremely interesting paper in this issue of AIDS, Law et al. [1] predict what effect HAART will have on reducing new HIV infections in the gay community in Australia. To make their predictions Law and colleagues [1] used a mathematical model that speci®es the transmission dynamics of HIV and the potential treatment effects of HAART. Transmission models can be useful health policy tools, because they can be used to provide a quantitative evaluation of the likely range of epidemiological outcomes. Such models can also be coupled with sophisticated uncertainty and sensitivity analysis techniques in order to be used as predictive tools [2]. The ®rst transmission model was constructed by Daniel Bernoulli over 200 years ago, and was used to evaluate the consequences of different interventions for the control of smallpox. Transmission models are dynamic process models, because they are constructed to contain the causal processes that generate epidemiclevel data such as incidence rates, death rates and prevalence. Dynamic process models are commonly used, and widely accepted, in the pure sciences, such as physics and chemistry. Such models are also used widely in many applied ®elds such as economics, demography, ®sheries management, geology, hydrology and climatology. However, transmission models have not yet been widely applied as either health policy or predictive tools in the study of infectious diseases.