Public health surveillance is the systematic, ongoing assessment of the health of a community, based on the collection, interpretation, and use of health data. Surveillance provides information necessary for public health decision making. This text presents an organized approach to planning, developing, and implementing public health surveillance systems. It has a broad scope, discussing legal and ethical issues as well as technical problems. It goes beyond the surveillance of particular conditions to the basic elements common to the application of surveillance to any type of health-related problem. The Second Edition has been updated throughout and many chapters have been expanded. Several new chapters have been added on the changing healthcare information infrastructure, quality surveillance, pharmaceutical surveillance, and the use of surveillance information in marketing and advocacy. The standard text in this field, it will continue to serve as a textbook for public health students and a desk reference for public health practitioners.