In 2013, MHRP initiated the African Cohort Study (AFRICOS), the first of its kind in sub-Saharan Africa. AFRICOS is a large long-term observational cohort study in Kenya, Nigeria, Tanzania, and Uganda. AFRICOS participants are enrolled from health facility clinic patient populations and allows for the unparalleled longitudinal characterization of the HIV epidemic in the African context, tracking the impact of clinical practices, biological factors and socio-behavioral issues on HIV and disease progression. AFRICOS findings influence host-nation HIV policy and PEPFAR programming by providing data for evidence-based guidelines and interventions.