HIV incidence remains unacceptably high in sub-Saharan Africa, with 2.5 new infections for every individual placed on treatment . Combination HIV prevention therefore remains a priority. Behavioural interventions remain the cornerstone, and changes in sexual behaviour have contributed to declines in HIV incidence in some settings [2, 3]. Male circumcision reduces HIV transmission by roughly 60 percent [4, 5], and voluntary medical male circumcision (VMMC) is being scaled up in 14 sub-Saharan African countries . The global community has pledged to eliminate mother-to-child transmission . Antiretroviral treatment can reduce risk of HIV acquisition and infectivity, and thus transmission between serodiscordant sexual partners [8, 9]. Research in sub-Saharan Africa will evaluate the population-level impact on HIV incidence of strategies to expand HIV testing and offer treatment to all who test HIV-positive and, perhaps, as pre-exposure prophylaxis to uninfected individuals.
HIV prevention programmers seek to effectively utilize resources to reduce HIV incidence and disparities in risk. Among this group there is widespread recognition that characteristics of the social, economic, legal, and cultural environment shape HIV epidemiology [10–15]. These “structural factors” are beyond the control of individuals but can affect infection rates for whole populations by influencing the environment in which people live . These same factors create and re-enforce social stratification within populations: for example, they generate economic or gender inequalities. Groups generated by these stratification processes (for example, the poor and the wealthy) are exposed to different social determinants of HIV risk . Parkhurst uses the term “structural drivers” to refer to determinants for which there is empirical evidence of an influence on HIV risk. These patterns of exposure may in turn be reflected in the social distribution of infections within a population (the social epidemiology of HIV). “Structural factors” have therefore influenced the pattern and scale of HIV epidemics and have constrained the delivery and effectiveness of HIV prevention, care, and treatment programmes (see Figure 1). Yet HIV prevention programmers still rarely include a “structural approach” when allocating resources.