The ultimate goal of this project is to incorporate a RNA-based diagnostic technology (called transcriptional signatures) to distinguish between bacterial and non-bacterial infections in otherwise well-appearing febrile infants who present to the EDs. The project aims to create a PECARN wide infrastructure for conducting translational genomic research and demonstrate feasibility of screening, consenting, collecting, and processing of small volumes of blood samples to abstract high quality RNA from febrile infants. After initially defining bacterial and non-bacterial biosignatures, we will conduct a limited validation of these diagnostic biosignatures on an independent group of febrile infants. Patient enrollment began in 2008 and continued through May 2013. Analysis is in progress. This project is co-funded by NICHD.