Topic overview

Start with the big picture

Outbreak investigation often requires more than a description of who became ill, where cases occurred, and when they appeared. Analytic epidemiology examines whether exposures differ between people who became ill and those who did not. These comparisons can help investigators assess whether a suspected source is associated with illness and how an infectious agent may have spread. Findings must be interpreted in the context of the outbreak evidence rather than treated as proof on their own. This topic focuses on the role of analytic comparisons in developing and evaluating explanations for an outbreak. It introduces the connection between exposure, source identification, and transmission without replacing the broader investigative process.