Key Epidemiological Terms

Patterns of Infectious Disease

Epidemic

Epidemic: The occurrence in a community or region of a group of illnessess of similar nature, clearly in excess of normal expectancy, and derived from a common or from a propagated source.

Example: Pertussis (whooping cough) is an acute bacterial respiratory disease that can cause severe coughing, especially in young children. It is a vaccine-preventable disease. Outbreaks of pertussis occurred in several Missouri counties in 2003 and 2004. In Schuyler County, the case rate rose from 0 in 2003 to 695 per 100,000 population in 2004.