The ongoing, systematic use of routinely collected health data to guide public health action in a timely fashion. Health surveillance tracks and forecasts the occurrence of health events or determinants through ongoing data collection. It also involves the collation, analysis and interpretation of those data into a product that is disseminated to those who need to know.

The periodic medical screening of a defined population for a specific disease or for biological markers of disease for which the population is, or is thought to be, at significantly increased risk. The program should include a mechanism to refer for treatment those persons who test positive for disease (also called Medical Monitoring).

(surveillance de la santé) The tracking and forecasting of any health event or health determinant through the continuous collection of high-quality data, the integration, analysis, and interpretation of those data into surveillance products (for example reports, advisories, alerts, and warnings), and the dissemination of those surveillance products to those who need to know. See also: health prevention, health protection, health promotion, and population health assessment