What is a case definition in disease surveillance?

• A. A set of laboratory protocols for testing.
• B. A method for diagnosing diseases in the clinic.
• C. A standardized criteria for classifying a person as having a disease; it ensures consistent reporting, comparability, and valid analyses.
• D. A policy for hospital billing.

Answer: (C)

A case definition in disease surveillance is a standardized set of criteria used to classify whether a person has a disease for reporting and analysis. This standardization ensures reports are consistent across different places and times, allowing reliable comparisons, trend detection, and valid analyses of outbreaks. A case definition may include clinical features (such as symptoms), laboratory evidence, and sometimes location or time frames, helping distinguish true cases from non-cases for the purpose of surveillance. For example, a surveillance influenza case might require fever and cough during flu season, with a lab-confirmed case added when a positive test is present. The other options describe laboratory testing procedures, routine clinical diagnosis, or hospital billing policies, which are not about classifying cases for surveillance.