Introduction: the Centers for Disease Control and Prevention's Epi-Aids--a fond recollection.

The Epidemic Intelligence Service (EIS) has served the United States and the world for >58 years by being an extraordinary apprenticeship in the fundamentals of practical field epidemiology: a training program, a professional entry point, the basis for lifelong careers, and a closely supervised and mentored opportunity for research, analysis, and community service. Epidemic-assistance investigations, a key element of the EIS experience, are the written summaries of each field investigation undertaken by the EIS officer. The resulting reports enter the record of the Centers for Disease Control and Prevention (CDC), provide scientific feedback to the state and locality where the epidemic or health problem occurred, and often form the basis for a subsequent manuscript to be submitted to a peer-reviewed medical journal. The EIS Program was created in 1951 to be a defense against potential bioterrorism, serve the immediate needs for field investigation, and provide for future workforce demands by combining epidemiology and laboratory science. During the past 60 years, CDC and public health practitioners have broadened their areas of responsibility by adding programs in reproductive health, environmental health, chronic diseases, nutrition, injury control and prevention, and noncommunicable disease risk factors. Epidemic-assistance investigations have evolved similarly. The papers in this Journal supplement reflect the evolution of public health responsibilities and the growth and development of CDC. They are a testimony to the value of clear, concise information and analysis, communicated to those who need to know as a public health and societal good.