Surveillance (Encyclopedia of Public Health)
Health surveillance is the ongoing, systematic use of routinely collected health data to guide public health action in a timely fashion. Surveillance systems count health events (e.g., deaths from a disease or new cases of a disease) and health services (e.g., visits to a doctor, hospital admissions, vaccination, surgery, provision of prescription drugs) as they occur. Some systems collect information on risk factors related to various diseases, including foods, water supply, drug use, and travel, while other systems measure health behaviors (e.g., smoking, alcohol and drug use, nutrition) and environmental factors (e.g., air, food, or water quality) independently of any health events associated with them
At the local level, health authorities receive detailed health information, often including names and addresses, because they have a mandate to provide services such as water testing, immunization, education, or referral to health agencies and services. As local authorities pass data to regional and national health departments, the data become less detailed. National data are usually anonymous. After collation, local, provincial, and national health departments tabulate, graph, and map cases in an effort to identify patterns of disease or risk factors, and to guide their actions. Routine reports normally include total case counts for specific time periods and populations, grouped by characteristics such as age, sex, or residence. Where population denominators are known, incidence rates of diseases are reported. With the wider availability of the Internet, many developed countries have implemented automated systems for the exchange, mapping, and analysis of surveillance data.
The first health surveillance activity is attributed to John Graunt, who first summarized causes of death in London in 1662. Today, surveillance exists for many infectious and chronic diseases, injuries, adverse reactions to drugs and vaccines, behavioral risk factors, and animal diseases. Most countries publish national data on a weekly or monthly basis for communicable diseases, and annually for causes of death. The World Health Organization (WHO) publishes causes of death and data on a few diseases on a global basis, using internationally accepted case definitions. In these ways, health surveillance provides health departments and related agencies with ongoing measurements of health of populations. Surveillance data have the same value to health departments and other interested groups (such as drug companies) as financial data do to commercial enterprises.
In the twentieth century, there were significant gains in global health as a result of immunization, made possible because routine surveillance of infectious diseases identified the important causes of childhood infections. Furthermore, continued surveillance after the introduction of vaccines has monitored the effectiveness of immunization programs. Perhaps the most impressive example of this was the WHO program for the elimination of smallpox. This program used intensive worldwide surveillance to identify all suspected cases of smallpox. Specialized teams then confirmed the diagnosis and instituted immunization programs in the population surrounding each case. Surveillance data were also used by many countries to justify elimination of routine smallpox vaccination programs as the number of new cases diminished. This program of public health action directed by surveillance led to the eventual elimination of this devastating disease in 1977.
(SEE ALSO: Assessment of Health Status; Epidemiology; Graunt, John; Information Technology; Internet; Notifiable Diseases; Registries; Surveys)
Teutsch, S. M., and Churchill, R. E., eds. (1999). Principles and Practices of Public Health Surveillance. New York: Oxford University Press.
World Health Organization (1992). International Statistical Classification of Diseases and Related Health Problems (ICD-10), 10th revision. Geneva: Author.