1.2 Purpose of surveillance

Surveillance should be conducted for a specific purpose, central to which is the public health question that the collected surveillance data will be used to answer. Consequently, if a surveillance program is not created around a specific question, or questions, that it will answer, then it is a poorly constructed surveillance system. The surveillance methods and data sources must be matched to the specific goals of the surveillance.

Surveillance systems are set up to perform one or more of the following:

• Provide information that can be used for health action by public health personnel, government leaders and the public.
• Underpin public health policy, set priorities and guide interventions to tackle issues of public health concern.
• Serve as an early warning system and a central pillar of public health emergency preparedness.
• Understand disease dynamics, patterns, seasonality, risk factors (aid understanding of disease epidemiology).
• Assess the impact and effectiveness of interventions and strategies to tackle public health issues.
• Develop hypotheses relating to risk factors of disease, which can be explored through analytical studies and research.

Surveillance forms the foundation for public health action to improve health outcomes. This function calls for surveillance to operate under a mandate of global, national or regional governmental organisations to secure the health of the public. High-quality evidence gathering is central to meeting this mandate and is made possible by good-quality surveillance. The information gathered from surveillance allows local and regional agencies, governments and global organisations to respond quickly and effectively to public health threats and concerns as they develop (Smith et al., 2013).

Surveillance infrastructure is central to good-quality surveillance. National governments, in liaison with global organisations (e.g. the World Health Organisation (WHO), Food and Agricultural Organisation of the United Nations (FOA), and the World Organisation for Animal Health (OIE)), encourage the development of national action plans for different diseases. These national plans typically lay out the strategic framework for developing and maintaining national-level surveillance infrastructure. Governing bodies and public health practitioners (at national and local levels) use this ‘direction’ to inform the development of strategic frameworks to guide and prioritise surveillance systems, according to their local context and resources.

Designers and users of surveillance systems have to ensure that these systems are flexible and agile enough to be able to respond to ever-evolving public health demands and corresponding statutory requirements. Surveillance systems also need to be able to adapt to advances in information technology – these can allow for increasingly rapid and cheap data collection, analysis and dissemination to help direct and support health care policy.

Before concentrating on the types of surveillance systems out there, let us discuss the important terms we need to familiarise ourselves with when discussing surveillance.