Project Summary Ideally, the utilization of point-of-care (POC) diagnostics to facilitate early clinical decision-making for infectious disease agents requires compatibility in both developing and developed settings. Herein, we propose to exploit a novel localized surface plasmon resonance (LSPR) digital sensing technology to provide low cost, simple to use (single-step, no wash step assay), rapid (15-20 minutes), highly sensitive (<1ng/mL), and quantitative diagnostics compatible with a diverse range of POC settings and infectious diseases. The metallic thin-film sensors are composed of alternating layers of nano-structured gold and dielectric that emits a highly reproducible and stable plasmon upon exposure to white light that confers a distinct color to the thin-film. When specific biomarkers are localized to the sensor surface they interfere with the plasmon resulting in corresponding color changes that are digitally-monitored with a simple camera-based optical reader using RGB and proprietary algorithms to enable both high-sensitivity and precise quantification of a target biomolecule in a sample. Furthermore, unique to the LSPR sensing platform is the exceedingly short sensing range (localized at and extending a few tens of nm from the surface) that enables a single-step assay format (no wash necessary), which considerably simplifies disposable cartridge design. In this proposal we detail plans to provide POC diagnostics for acute dengue and Zika virus infection. The sensors will be integrated into a small fluidic assay cartridge that utilizes simple passive capillary action to move sample to the sensing region to selectively detect flavivirus specific NS1 proteins from serum in a rapid 20 minute assay format. We further propose herein to provide a versatile, low cost and robust hand-held portable camera-based digital reader compatible across a diverse range of POC settings. The reader will contain blue-tooth and Wi-Fi functionality, and a user-friendly interface with proprietary software to detect and quantify the LSPR signal / viral NS1 antigen. Prototype diagnostics will be validated against dengue and Zika patient serum samples to determine sensitivity. Furthermore, the dengue and Zika patient samples as well as normal and other infectious disease serum samples will be used to test for cross-reactivity (i.e. specificity). The goal is to provide a working alpha-prototype that demonstrates ≥90% sensitivity and specificity.