The WADA (West Africa Data Base on Antiretroviral Therapy) Collaboration is a unique collaboration among cohorts in West Africa with a mission to conduct hypothesis-driven epidemiological research on the prognosis and outcomes of HIV-1 and HIV-2-infected people, including adults, pregnant mothers, adolescents and children in care and generally on treatment, as well as HIV-exposed children. Our five- year research plan will focus on scientific questions that the contributing cohorts cannot answer individually and which do not overlap with existing projects. During the five years of the next IeDEA round, the overall aims of WADA are: 1) to measure trends and characteristics of antiretroviral treatment (ART) initiation in different HIV programs throughout West Africa. This will follow the adoption of the new 2015 WHO guidelines promoting universal tests and treat; 2) to characterize the strategies used at site and country levels to increase the degree of viral load suppression among HIV-infected adults and children on ART: a) changes in routine and targeted prescription of HIV plasma viral load; and b) improvements in both the retention in care and adherence to ART; 3) to document the trends in ART response and impact in HIV- infected specific populations, focusing on adolescents transitioning in care, individuals with hepatitis B co- infection, HIV-2 infected patients and women of reproductive age especially on the relationship between HIV care and reproductive health services. To date, the pooled database assembled by the WADA Collaboration in the current IeDEA cycle includes 84,594 HIV-1 infected adults and 6,043 HIV-infected children who initiated ART in 28 clinics; in addition the database also includes data from 5,209 HIV-2 or HIV1&2 infected adults of whom 3,984 are on ART. The next round will involve 22 HIV clinical centers (adults: 12, pediatrics: 10) in eight countries (Benin, Cote d'Ivoie, Ghana, Guinea Bissau, Mali, Nigeria, Senegal, Togo). Among them, two adult clinics and one pediatric clinic are new collaborating centers. WADA is coordinated at the Bordeaux School of Public Health (ISPED) in Bordeaux University, France with a WADA Regional Office hosted by PAC-CI, a research-oriented non-governmental organization situated in Abidjan, Cte d'Ivoire. This research team has a long-lasting experience in observational HIV research including large-scale prospective cohorts in West Africa. Data will be collected from affiliated cohorts every year according to standardized procedures and will be merged at the Coordinating Center in Bordeaux. Capacity building in participating centers will include funding for local human resources, training on data quality, on-site technical support and annual meetings to reinforce the technical and scientific network. The priority research agenda will address the following topics:, trends in ART initiation and response, retention in care, natural history of HIV-2 and HIV-1/HIV-2 infections, cancer, hepatitis B co-infection, mental health, pregnancy outcomes, adolescent and pediatric access and quality of care.