Surveillance in epidemiology is best described as:

• A. A cross-sectional survey at a single time
• B. Ongoing systematic collection, analysis and interpretation of health data to prevent disease
• C. Experimental trial in a laboratory
• D. Passive reporting only by patients

Answer: (B)

Surveillance in epidemiology is an ongoing, systematic process of collecting, analyzing, and interpreting health data to guide public health actions and prevent disease. It isn’t just a one-time snapshot or a single report; it continually gathers data from multiple sources, analyzes trends, and disseminates findings that trigger interventions, alerts, or policy changes to protect health. This proactive, data-driven use of information is what sets surveillance apart from a one-off cross-sectional survey, an experimental trial, or simple passive patient reporting.