Forty-six EDs, two major pharmacy chains, two poison control centers and the Centers for Disease Control and Prevention (through a pilot partnership), all contribute data to ESSENCE on a daily basis. Data reported from June 1, 2009, through January 1, 2011, were used to examine the relationships between ED visits for ILI and antiviral (M2 inhibitors and neuraminidase inhibitors) prescription medication transactions in the state of Maryland. ArcGIS 9.2 was used to spatially evaluate these relationships. Data for the total population of Maryland by jurisdiction were obtained from the U.S. Census Bureau, Census 2010 PL94-171 release and prepared by the Maryland Department of Planning, Projections and Data Analysis/State Data Center, April 2011.