Abstract
This study compared weekly percent of influenza-like illness (ILI) in Early Notification of Community-based Epidemics (ESSENCE) to weekly counts of laboratory confirmed influenza cases and evaluated the early warning potential of the ESSENCE weekly ILI percent for five consecutive influenza seasons (2006-11) in Missouri. ESSENCE weekly ILI percent was significantly correlated with weekly counts of laboratory-confirmed influenza cases. Use of the ESSENCE percent ILI baseline provided two weeks of advanced warning for seasonal influenza activity. These findings justify the use of ESSENCE for influenza surveillance.