Topic overview

Start with the big picture

Descriptive epidemiology examines health events by person, place, and time. A time-based description can distinguish long-term movement from recurring seasonal patterns and the shorter-term shape of an outbreak. Secular trends refer to changes observed over an extended period, while seasonal variations describe patterns that recur in relation to seasons. Epidemic curves present the timing of cases during an outbreak, helping describe its progression. This introductory topic focuses on recognizing these different time scales and the role each plays in describing population health patterns. It provides a foundation for interpreting temporal observations without treating a pattern alone as proof of its cause.