The global HIV pandemic has evolved into a complex mosaic of epidemics within and between countries, with no single solution for preventing HIV infection. Increasing access to antiretroviral treatment has reduced AIDS-related mortality and morbidity rates, but—with nearly three million new infections each year—we are losing the HIV prevention battle (Joint United Nations Programme on HIV/AIDS [UNAIDS] 2008), primarily in sub-Saharan Africa.
For prevention efforts to succeed, prevention programming must be tailored to the specific characteristics of the epidemic that is unfolding in the area to be targeted. Assessing an epidemic at the local or regional level is an important first step to enhancing and customizing prevention responses. This requires a nuanced understanding of who is at highest risk of infection and what drives that risk. With this information, program planners can determine who the target populations are and how to reduce risk with evidence-based interventions that are appropriate and acceptable and that have proven ability to reduce HIV incidence.