[Basic aspects of public health surveillance for the 90s]

In this paper we propose a wider scope for public health surveillance in order to incorporate demographic and health systems monitoring along with activities conventionally associated with epidemiologic surveillance. This new conception stems, in turn, from a revised definition of public health, which describes--not a sector of activity or a type of health service--but a level of aggregation based on the population at large. In our review of the ideas that lead to the institutionalization of health surveillance, we stress the broad concepts developed by such pioneers as Graunt and Petty. Their original concepts emerged from their active concerns for the public's health at a time when no scientific theory of contagion was available--let alone any knowledge about how to treat persons for the major diseases that affected them. Later on, and largely as the result of impressive advances in biomedical knowledge, surveillance activities tended to specialize and to concentrate predominantly on disease outbreaks and on salient adverse health conditions. Health surveillance became closely associated with epidemiologic surveillance, which in turn became associated with the ability to respond promptly to adverse health outcomes. Recently, we have witnessed a gradual broadening of both the concepts and the practice of health surveillance. Paradoxically, the newer proposals tend to recapture part of the spirit and scope of earlier definitions, prompted perhaps by such thoughtful historic parallels as the newly emerging health problems for which we have no clear-cut solution. If one element has to be stressed to promote the objectives of health surveillance today, it is the need to anticipate health outcomes and not just respond to them. This, in turn, requires an increased attention to the surveillance of risk factors, and a greater understanding of the complex causal relationships that those factors--including behavioral, lifestyle, and environmental ones--with adverse health outcomes and disability. Needless to say that, the first and foremost aim of health care--and of modern surveillance--is to promote the well-being of individuals by improving their health.