PROJECT SUMMARY/ABSTRACT Background. As sub-Saharan African (SSA) countries embark on the last mile toward HIV elimination, HIV programs must prioritize hard-to-reach mobile populations at the greatest risk of HIV acquisition and onward transmission. Some differentiated service delivery models may work for mobile people, but targeting services to such a broad category of individuals could waste limited resources. Since it is unclear which forms of mobility most significantly increase the risk of HIV infection, this study aims to systematically characterize mobility and relate it to HIV incidence at both the individual and sexual network levels. Aims. In line with NIMH Human Mobility and HIV program objectives to determine incidence rates and examine HIV outcomes among mobile populations, this study will 1) characterize mobility and its association with HIV testing and viral load suppression, 2) estimate HIV incidence by mobile group, and 3) determine the effect of mobility on the risk of HIV acquisition in sexual networks. Elucidating these gaps will inform future targeting and tailoring of interventions to improve the health of mobile populations. Approach. Since no consistent measure for mobility exists across HIV studies in SSA, this research will use detailed mobility metrics from the Rakai Community Cohort Study (RCCS), a population-based longitudinal study in south-central Uganda where there is substantial human movement, to develop a multidimensional measure that considers the frequency, duration, motivation, and spatial dimensions to people’s movement. This measure will uncover subclasses of mobility that can be linked to HIV incidence and other prevention and treatment outcomes. RCCS data from 19,300 adults aged 15-49 will be supplemented with data from Hard-to-Reach (HTR), an embedded study within the RCCS that captures HIV outcomes and mobility patterns among 2,000 individuals who have been lost to follow-up (LTFU) in the RCCS. This presents a unique opportunity to assess the missing data biases introduced by population mobility in open, dynamic cohorts. Each Specific Aim will use the full extent of the available data, including longitudinal HIV biomarkers and detailed contact investigations conducted among HIV incident cases and their HIV-negative matched controls. Training. Ms. Khalifa’s training plan leverages her quantitative abilities and HIV research experience to advance her skills and launch her into a career as an independent investigator focused on mobility and health. Her training goals are to develop in-depth knowledge of mobility and migration, gain experience with longitudinal survey methods, learn advanced epidemiologic techniques for missing data and network analyses, and build capacity for effective research dissemination. Under the guidance of her Primary Sponsor, Ms. Khalifa will receive tailored mentorship from a team of experienced HIV researchers who work with the parent studies, conduct mobility-focused research,...