Which statement correctly distinguishes prevalence from incidence?

Which statement correctly distinguishes prevalence from incidence?

• A. Prevalence measures new cases over time; incidence measures existing cases at a point.
• B. Prevalence at one point in time; incidence over a period of time.
• C. Incidence equals prevalence in a steady-state population.
• D. Prevalence is the proportion of people with disease at a given point in time, while incidence is the rate of new cases over a period in those at risk.

Answer: (D)