In disease surveillance, what is a case definition?

• A. A laboratory test protocol used to confirm disease.
• B. A standard set of criteria used to classify whether a person has the disease for surveillance, typically including person, place, time, and clinical criteria.
• C. A list of all reported cases in a region.
• D. A vaccination eligibility checklist.

Answer: (B)

A case definition is the standardized set of criteria used in disease surveillance to decide whether an individual is considered a case for reporting and monitoring. It brings together factors like who is affected (person), where the exposure or event occurred (place), when it happened (time), and the clinical features or symptoms observed. This uniform framework lets health professionals classify cases consistently across different locations and times, which is essential for accurate trend analysis, outbreak detection, and comparing data.

Lab results can play a role within a case definition (to label a case as confirmed or probable), but the definition itself is broader than any single test and is meant to guide decision-making about classification, not just verification. The other options describe components that aren’t about defining who is a case for surveillance—one is just a testing protocol, another is a list of reported cases, and the last is a vaccination eligibility checklist.