Background: Increasing HIV testing and entry into prevention services remains an important public health goal, in addition to reducing disparities in the incidence of HIV and treatment outcomes. In this study, we will examine environmental influences on HIV risk/transmission and treatment and prevention. The data we collect will inform our plans to use our section s geographical and predictive analytics in a new way, predicting where HIV prevention efforts should be targeted on a time scale of weeks or months. This is a question of interest to the Baltimore City Health Department, among others, and the 472 protocol provides the most efficient and logical way for us to begin collecting the relevant data.