Disease Surveillance
~2 min read
Lesson 12 of 20
Notes
Disease surveillance is the ongoing, systematic collection, analysis, and interpretation of health data, essential for planning, implementing, and evaluating public health practice. Without surveillance, public health authorities cannot detect outbreaks, track trends, or allocate resources effectively.
Two broad types of surveillance exist: indicator-based and event-based. Indicator-based surveillance involves monitoring specific selected health indicators — often specific notifiable infectious diseases (such as tuberculosis) or cancers — and reporting rates by person, place, and time. Event-based surveillance involves organised monitoring of reports, media stories, rumours, and other information about health events that could pose a serious risk to public health.
Within indicator-based surveillance, three subtypes are distinguished:
Passive surveillance is the routine reporting of health data by health providers to health authorities. Data sources include notifiable disease registers (clinicians are legally required to report specified diseases), disease registries, and hospital data. It is the most common type. Strengths: low cost; covers a wide area simultaneously (e.g., all hospitals reporting nationally); enables data linkage. Weakness: under-reporting is a major concern — not all cases are detected or reported.
Active surveillance occurs when health authorities actively seek health information rather than waiting for it to be reported. Methods include serosurveillance (testing blood samples for specific antibodies or antigens) and health surveys (actively identifying cases). Strengths: may provide more complete and timely data. Limitations: resource-intensive and expensive; health surveys are impractical at national scale.
Sentinel surveillance involves monitoring the health of individuals at specific selected sites (e.g., a sample of GP clinics, selected hospitals, or specific geographic areas) to provide an indication of trends in the wider population. For example, sentinel GP clinics may report influenza cases during winter to estimate community flu burden. Used to monitor trends and detect outbreaks.
A good surveillance system is timely, sensitive (detects cases and outbreaks), specific (correctly classifies cases), representative, simple, flexible, acceptable to participants, and stable.