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Public health surveillance is the cornerstone of public health practice, generating vital information for decision-making in nearly all aspects of public health work. Public health surveillance has been defined as “the ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice, closely integrated with the [timely] dissemination of these data to those who need to know and linked to prevention and control.”1 Important in this definition is the requirement that surveillance activities be closely aligned with public health actions to prevent and control disease, promote population health, and reduce health inequities.

Public health surveillance serves many purposes (Box 7-1). Surveillance is the primary means by which disease outbreaks are identified, characterized, and monitored to ensure effective control. Surveillance data are used to identify and address emerging health threats. Recent notable examples include the rapid spread of Zika virus in the South Pacific and the Americas beginning in 2007 and 2015, respectively,2 the Ebola viral disease outbreak in West Africa in 2014,3 and the rapid global spread of a novel new coronavirus (SARS-CoV-2) beginning in late 2019.4 Surveillance is also important for detecting the resurgence of old threats, such as the steep increase in sexually transmitted infections in the United States beginning in 2013.5 The importance of surveillance in protecting the public against acute health threats extends beyond communicable diseases to also include toxic environmental exposures, such as lead poisoning.6

Box 7-1 Purposes of Surveillance

  • Detecting and monitoring responses to disease outbreaks and epidemics

  • Characterizing the natural history of disease

  • Quantifying the magnitude of a health problem and monitoring trends over time

  • Characterizing the geographic distribution of disease

  • Identifying at-risk groups

  • Monitoring patterns of antimicrobial resistance

  • Detecting and monitoring responses to environmental hazards in community and workplace settings

  • Identifying and characterizing health disparities

  • Characterizing and tracking conditions in the environment that impact health, including the natural environment, built environment, and social environment

  • Monitoring the safety of medical products

  • Monitoring healthcare practices

  • Supporting program planning, priority setting, and resource allocation decisions

  • Informing policy development

  • Evaluating impacts of public health programs and other interventions

  • Generating causal hypotheses

  • Supporting education and advocacy

Surveillance also supports health-promotion efforts, providing essential information on the incidence and prevalence of chronic health conditions, related health behaviors, unintentional injuries, and violence. In addition, surveillance is used to characterize and track the underlying conditions in community environments that impact health, including the social determinants of health.

Surveillance data provide important information for establishing public health priorities and determining how to best allocate resources. Surveillance information is used to inform program planning and policy development. Once programs and policies are implemented, surveillance data can be used to assess their impacts. Surveillance data are also often used to support advocacy efforts by helping to document the significance of a health issue in the ...

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