The Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE) is used in the early detection of infectious disease outbreak and provides epidemiological tools that can be used to investigate disease oubreaks. It utilizes ambulatory data from hospitals and clinics. Epidemiologists can track, in near real-time, symptoms being reported in a region through a daily feed of reported data (such as working diagnoses indicated by codes assigned by local health care staff). ESSENCE uses the daily data downloads, along with traditional epidemiological analyses that use historical data, for baseline comparisons in order to improve detection.