Which statement best describes the difference between incidence and prevalence and their use in public health surveillance?

• A. Incidence is the number of new cases over a time period divided by the population at risk; reflects risk.
• B. Prevalence is the number of new cases over a time period divided by the population at risk.
• C. Incidence equals the total number of existing cases at a given time.
• D. Incidence and prevalence measure the same concept.

Answer: (A)