Health officials monitor and investigate food-borne illness in a number of ways. Surveillance is used to track trends in the incidence of several common bacterial and parasitic food-borne illnesses. Tracking of outbreaks of food-borne illness helps improve approaches to investigation. Genetic "fingerprinting" is also used to identify infections from a common source, including large multistate outbreaks. Collectively, these tools shed light on the burden of food-borne illness in the U.S., and ways to decrease it. This book examines several systems to monitor food-borne illnesses, discussing their strengths and the gaps that remain in understanding the burden of food-borne illness in the United States, with a focus on E. coli and salmonella.