The proposed project involves the evaluation, optimization and extension of North Carolina's Screening and Tracing of Active Transmission Program (STAT). As presently implemented statewide, the STAT Program encompasses all publicly funded routine HIV counseling and testing in NC (n= 120,000 annually). STAT provides for detection of very early acute HIV infections in this population by using novel specimen pooling and HIV RNA detection methods in a central State Laboratory of Public Health. Cases of acute HIV identified by these methods trigger initiation of immediate confirmatory testing, network notification and partner screening by a special team of professional Disease Intervention Specialists. The STAT program is prospectively collecting extensive data on acute cases and their contacts, thereby providing a unique window on active HIV transmission taking place over a large geographic area. The proposed research described in this application capitalizes on these data in order to address significant gaps in our current understanding of HIV transmission and its prevention. We have assembled an experienced team of investigators in order to: 1. Evaluate the impact and performance of a large scale, primary care-based acute HIV screening and partner notification program; 2. Characterize acute HIV infection as it presents in NC's routine testing population, and develop diagnostic strategies for targeting primary care-based acute HIV screening; 3. Describe a population of HIV positive individuals who are either knowingly or unknowingly transmitting HIV in NC communities; and 4. Perform detailed cost effectiveness modeling in order to optimize acute HIV-centered efforts at HIV prevention.