Statistical principles of monitoring and surveillance in public health.

Monitoring and surveillance are seen as statistical procedures that will help health authorities to achieve better health services with the existing resources-monitoring being an integrated system of making observations on health and environmental factors and of scrutinizing, storing, and retrieving those data, and surveillance being a closely associated system for collating and interpreting the data.Monitoring should be an action oriented activity and may encompass a wide range of health activities, for example, communicable and noncommunicable diseases, environmental pollutants, and specific problems in health care delivery systems. Both monitoring and surveillance systems have to be related to control measures, and, since the available resources are usually limited, a scale of priorities has to be developed by the statistician in cooperation with the competent authorities.MONITORING MAY BE PERFORMED ON EITHER THE INDIVIDUAL OR AGGREGATE LEVEL AND SHOULD BE PLANNED TO TAKE INTO ACCOUNT THE COURSE OF THE DISEASE UNDER CONSIDERATION: it is concerned with monitoring stimuli and events. Collection of data, for example, on exposure to a pollutant, may be continuous and automatically recorded, or regular or irregular through population sampling or registries. The statistical requirements of monitoring and surveillance systems are discussed and a checklist of features to be considered is given in an annex.