Distinguish prevalence from incidence in epidemiology.

• A. Incidence is the proportion of a population that has the disease at a given time.
• B. Prevalence is the rate of new cases developing over a defined period.
• C. Prevalence is the proportion of a population with disease at a given time; incidence is the rate of new cases over a defined period.
• D. Incidence is the number of existing cases at a specific time.

Answer: (C)