Public health surveillance and knowing about health in the context of growing sources of health data.

The past decade has brought substantial changes in how data related to a community's health are collected, stored, and used to inform decisions about health interventions. Despite these changes, the purpose of public health surveillance has remained constant for more than a century. Public health surveillance is the ongoing, systematic collection, analysis, and interpretation of health-related data with the a priori purpose of preventing or controlling disease or injury, or of identifying unusual events of public health importance, followed by the dissemination and use of information for public health action. Surveillance is an important and necessary contributor to knowledge of a community's health. The public health system is responsible for ensuring that public health surveillance is conducted with appropriate practices and safeguards in order to maintain the public's trust.