The epidemic of HIV-1C in southern Africa is characterized by a sustained prevalence that is substantially higher than for other epidemics of HIV/AIDS. Perhaps the best correlate of transmission is high viral load (HVL), which we target to prevent spread of HIV in a community randomization trial based on antiretroviral treatment (ART) as prevention (TasP). Designed for over 100,000 adults in 30 randomized villages in Botswana, this trial also utilizes other prevention interventions such as HIV testing, male circumcision, clinical linkage and ART chemoprophylaxis during pregnancy. Viral phylogenetics is used to estimate the proportion of incident infections originating in test villages, and thus the relative contribution of TasP for preventing transmissions. Analysis of results through modeling includes estimating cost effectiveness and estimations of contributions for different prevention interventions
