Radiation Monitoring Devices, Inc. proposes to design a simple, high speed, highly sensitive viral detection instrument. This instrument will measure fluorogenic reporter genes, which hybridize to complementary viral gene target inside a capillary waveguide. Our single-photon sensitive Geiger-mode, microavalanche photodiodes (micro-APDs) will enable low limits of detection of viruses. The micro-APD :an be battery-powered because of its low voltage requirement and rugged characteristics. We will also use active quenching circuitry, which allows measurement of a large dynamic range (-10 E 6), needed for continuous monitoring through exponential nucleic acid amplification. In Phase I, we will design the waveguide sensor, the micro-APD detection system, and establish fluorogenic probe chemistry. In Phase I, we will design a system for viral load detection, array formatting, establish nucleic acid amplification reactions, test a virus, and explore the instrument's versatility.