Case definition is based on metrics?

• A. Disease Signs, Symptoms, and Epidemiology
• B. Animal performance
• C. Mortality rate
• D. Genetic markers

Answer: (A)

Case definitions are standardized criteria used to determine who is considered a case for surveillance and research. The most foundational elements are the observable clinical features—signs and symptoms—together with the epidemiologic context, such as who is affected, where, and when, including potential exposures. These components allow consistent case ascertainment across settings and over time. Laboratory confirmation or genetic markers can refine or confirm cases, but they are not the primary basis for the general case definition. Options focusing on animal performance, mortality rate, or genetic markers alone do not provide the typical basis for defining cases in surveillance, which centers on how the disease presents clinically and how it spreads in the population.