Prevalence is best described as

• A. The proportion of the population with disease at a given time.
• B. The rate of new cases per person-time.
• C. The number of deaths due to disease in the population.
• D. The lifetime risk of developing the disease.

Answer: (A)

Prevalence describes the burden of disease in a population at a specific moment, expressed as the proportion of people who have the disease. It’s a count of existing cases divided by the total population, often shown as a percentage. This distinguishes it from incidence, which counts new cases over time and is a rate per person-time, and from mortality, which counts deaths, or lifetime risk, which estimates the chance of developing the disease over a lifetime. For example, if on a given date 150 out of 10,000 people have diabetes, the prevalence is 150/10,000 = 1.5%.