Objectives of Surveillance Systems
Public health surveillance provides the scientific and factual database essential to informed decision making and appropriate public health action. The key objective of surveillance is to provide information to guide interventions. The public health objectives and actions needed to make successful interventions determine the design and implementation of surveillance systems. For example, if the objective is to prevent the spread of epidemics of acute infectious diseases, such as SARS, managers need to intervene quickly to stop the spread of disease. Therefore, they need a surveillance system that provides rapid early warning information from clinics and laboratories. In contrast, chronic diseases and health-related behaviors change slowly. Managers typically monitor the effect of programs to change risky behaviors such as tobacco smoking or chronic diseases once a year or even less often. A surveillance system to measure the population effects of a tuberculosis control program might provide information only every one to five years—for example, through a series of demographic and health surveys. The principle is that different public health objectives and the actions required to reach them require different information systems The type of action that can be taken, when or how often that action needs to be taken, what information is needed to take or monitor the action, and when or how frequently the information is needed should determine the type of surveillance or health information system (box 53.1).
[Box 53.1]
