Public health surveillance is a critical component of every public health department or health ministry, and surveillance of disease continues to be a major topic in public health circles worldwide. The goal of public health surveillance is to reduce the spread of disease among the population and to provide public health officials with early warnings of threats to human health.

International public health organizations, such as the World Health Organization, have recently called for wider deployment of disease surveillance systems to protect nations. Organizations, such as the European Union Commission, have recently called for its 25 member countries to join in a new program for ensuring that public health surveillance systems interoperate across all European nations. The United States Centers for Disease Control and Prevention is presently engaged in building a national electronic disease surveillance system called the National Electronic Disease Surveillance System in all 50 states. The Ministry of China recently announced plans to develop a similar surveillance system across 30 provinces.

It is clear that nations, states, and local communities, as well as individual health practitioners, all play an important role in making sure that these comprehensive surveillance systems work and communicate the kind of knowledge that allows public health specialists to take action. Modern public health surveillance systems are capable of collecting, reporting, analyzing, and visualizing clinical information, such as symptoms and diagnoses, within analytical frameworks that assure accurate geographic representation of place—one of the three critical factors in epidemiology (people, time, and place). As the series of articles in this issue illustrates, disease surveillance is about communicating knowledge that leads to action.

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