The epidemiologic field investigation: science and judgment in public health practice.

Epidemiologic field investigations are often done in response to acute public health problems. When outbreaks of disease occur, there usually is an urgent need to identify the source and/or cause of the problem as a basis for control. Alternatively, the identification of environmental or occupational hazards frequently demands evaluation of exposed persons and assessment of the risks of disease. In this commentary, the authors present a perspective on the public-sector practice of epidemiology by considering the factors that influence epidemiologic prospectively planned studies; and examining the complexities of the relations between epidemiology and public health practice.