In 1963, Alexander D. Langmuir defined disease surveillance as" the continued watchfulness over the distribution and trends of incidence through the systematic collection, consolidation and evaluation of morbidity and mortality reports and other relevant data" and the regular dissemination of data to" all who need to know"(1, pp. 182-183). Langmuir was careful to distinguish surveillance both from direct responsibility for control activities and from epidemiologic research, although he recognized the important interplay among epidemiologic studies, surveillance, and control activities. In 1968, the 21st World Health Assembly held technical discussions on the National and Global Surveillance of Communicable Disease and identified these main features of surveillance: 1) the systematic collection of pertinent data; 2) the orderly consolidation and evaluation of these data; and 3) the prompt dissemination of the results to those who need to know, particularly those who are in a position to take action (2). Subsequently, the applications of surveillance concepts have broadened to include a wider range of health data—risk factors, disability, and health practices—as well as disease. This is reflected in the 1986 Centers for Disease Control (CDC) definition of epidemiologic surveillance:

Abbreviations: AIDS, acquired immunodeficiency syndrome; CDC, Centers for Disease Control; NCHS, National Center for Health Statistics; NIOSH, National Institute for Occupational Safety and Health; WHO, World Health Organization. 1 Center for Environmental Health and Injury Control, Centers for Disease Control, Atlanta, GA 30333.(Reprint requests to Dr. Stephen B. Thacker.) 2 Epidemiology Program Office, Centers for Disease Control, Atlanta, GA.