  In several countries in southern Africa, including South Africa, the
prevalence of HIV remains stubbornly high in spite of considerable efforts to
reduce transmission and to provide anti-retroviral therapy (ART). It is
important to know the extent to which the high prevalence of HIV reflects the
increasing number of people on ART in which case the prevalence of those not on
ART may be falling. Unfortunately, direct measures of the proportion of
HIV-positive people who are on ART are lacking in most countries and we need to
use dynamical models to estimate the impact of ART on the prevalence of HIV. In
this paper we show that the current level of ART provision in South Africa has
probably reduced the prevalence of HIV among those not on ART by 1.9 million,
averted 259 thousand new infections and 428 thousand deaths.

Quantitative Methods