Lesson 5: Public Health Surveillance

Section 2: Purpose and Characteristics of Public Health Surveillance

Public health surveillance provides and interprets data to facilitate the prevention and control of disease. To achieve this purpose, surveillance for a disease or other health problem should have clear objectives. These objectives should include a clear description of how data that are collected, consolidated, and analyzed for surveillance will be used to prevent or control the disease. For example, the objective of surveillance for tuberculosis might be to identify persons with active disease to ensure that their disease is adequately treated. For such an objective, data collection should be sufficiently frequent, timely, and complete to allow effective treatment. Alternatively, the objective might be to determine whether control measures for tuberculosis are effective. To meet this objective, one might track the temporal trend of tuberculosis, and data might not need to be collected as quickly or as frequently. Surveillance for a health problem can have more than one objective.

After the objectives for surveillance have been determined, critical characteristics of surveillance are usually apparent, including:

  • Timeliness, to implement effective control measures;
  • Representation, to provide an accurate picture of the temporal trend of the disease;
  • Sensitivity, to allow identification of individual persons with disease to facilitate treatment; quarantine, or other appropriate control measures; and
  • Specificity, to exclude persons not having disease.

Other characteristics of well-conducted surveillance are described in Appendix A. The importance of each of these characteristics can vary according to the purpose of surveillance, the disease under surveillance, and the planned use of surveillance data (See Table 5.7 in Appendix A). To establish the objectives of surveillance for a particular disease in a specific setting and to select an appropriate method of conducting surveillance for that disease, asking and answering the following questions will be helpful.

  • What is the health-related event under surveillance? What is its case definition?
  • What is the purpose and what are the objectives of surveillance?
  • What are the planned uses of the surveillance data?
  • What is the legal authority for any data collection?
  • Where is the organizational home of the surveillance?
  • Is the system integrated with other surveillance and health information systems?
  • What is the population under surveillance?
  • What is the frequency of data collection (weekly, monthly, annually)?
  • What data are collected and how? Would a sentinel approach or sampling be more effective?
  • What are the data sources? What approach is used to obtain data?
  • During what period should surveillance be conducted? Does it need to be continuous, or can it be intermittent or short-term?
  • How are the data processed and managed? How are they routed, transferred, stored? Does the system comply with applicable standards for data formats and coding schemes? How is confidentiality maintained?
  • How are the data analyzed? By whom? How often? How thoroughly?
  • How is the information disseminated? How often are reports distributed? To whom? Does it get to all those who need to know, including the medical and public health communities and policymakers? (9, 10)

References (This Section)

  1. Protocol for the evaluation of epidemiological surveillance systems [monograph on the Internet]. Geneva: World Health Organization [updated 1997; cited 2006 Jan 20]. Available from: http://whqlibdoc.who.int/hq/1997/WHO_EMC_DIS_97.2.pdf.
  2. Hopkins RS. Design and operation of state and local infectious disease surveillance systems. J Public Health Management Practice 2005;11(3):184–90.

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