Universal antiretroviral treatment for HIV and pre-exposure prophylaxis (PrEP) are highly effective and promising strategies to eliminate HIV spread. However, standardized approaches to treatment and prevention fail to meet the needs of diverse populations with diverse patterns of care engagement. Geographic mobility, including migration, work-related travel and other forms, has long been recognized as an important driver of the HIV epidemic, and more recently a risk factor for disruptions to HIV care. Emerging evidence suggests that mobility impacts risk differentially by sex, and that the drivers of mobility also differ by sex (including travel during pregnancy and postpartum for extended family support). However, the pathways by which mobility increases HIV risks remain poorly understood, thus hindering our ability to intervene to support engagement in care and prevention in mobile groups. The social contexts that drive mobility (e.g., gender roles, employment, illness, pregnancy), the home and destination environments (e.g., stigma, clinic access, sexual networks), and the duration, frequency, and timing of movement in relation to HIV risk factors, all require further investigation to enable appropriate interventions to be delivered in the right places and at the right times. Leveraging previously collected data from a 4-year community-based cohort of 2750 adults in East Africa, this proposed research aims to characterize how mobility and HIV risk factors are associated across space and time, with a lens towards differences by gender roles and forms of mobility, via three specific aims: (1) To characterize spatial relationships between higher-risk sexual behavior, viremia, and mobility in persons living with HIV, in association with HIV clinic locations, using mapping technology and geographically weighted regression analyses; (2) To identify latent subgroups with similar temporal patterns of higher-risk sexual behavior, viremia, engagement in care, and mobility among persons living with HIV, using group-based multi-trajectory modeling, a novel semi-parametric approach to identifying subgroups with similar behaviors or outcomes over time; and (3) To elucidate the role of mobility in attitudes and preferences regarding PrEP initiation and engagement in the perinatal period, using in-depth interviews and following a grounded-theory analytic approach. This research will generate new knowledge regarding spatial and temporal patterns of co-occurring risk factors for HIV transmission in mobile populations living with HIV, including the potential impact of mobility on PrEP use in the perinatal period. As a junior investigator focused on HIV and pregnancy in sub-Saharan Africa, the project director will gain expertise in mobility concepts, metrics, and analytic methods which will meaningfully enrich her future research within in this highly mobile population. Moreover, the findings from this proposed work will directly inform the development of an R01 application to examine targeted adherence support strategies for perinatal women living with and at risk of HIV.