Prevalence is the number of existing cases at a point in time. Which statement best reflects this concept?

• A. It measures new cases developing over time
• B. It is the number of existing cases at a point in time
• C. It equals the mortality rate
• D. It is the rate of disease spread

Answer: (B)

Prevalence tells us how widespread a condition is in a population at a specific moment by counting everyone who currently has the condition. This differs from incidence, which looks at new cases developing over time. Prevalence can be a raw count or a proportion of the population, and it reflects both how often new cases occur and how long people live with the condition (longer duration increases prevalence). It does not measure deaths (mortality) or how rapidly a disease is spreading (transmission). So the statement that best reflects prevalence is that it is the number of existing cases at a point in time.