This proposal is to develop a rapid method for separating, identifying and counting small numbers of viral pathogens from tissues, blood, urine, water supplies, and natural waters, with emphasis on agents currently unculturable. It is based on the observation that in nature there are few particles of viral dimensions that have a narrow range of both sedimentation rates and isopycnic banding densities, which are not viruses. In Phase I, a prototype centrifugal concentration and microbanding system was constructed and tested which employs a density gradient, density standards, laser illumination and staining with DNA-binding fluorescent dyes. Virus particles from 4 mL samples have been concentrated to a cubic micron, yielding PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE