Incidence vs. prevalence – which statement is correct?

Incidence vs. prevalence – which statement is correct?

• A. Incidence rate captures new cases over time, while prevalence rate captures all existing cases at a point or period
• B. Incidence rate captures all existing cases, while prevalence rate captures only new cases
• C. Both rates capture only new cases
• D. Both rates capture only existing cases

Answer: (B)

Understanding the difference between incidence and prevalence starts with what each measure counts. Incidence looks at new cases that appear in a population during a defined time period, giving a sense of the rate at which people are developing the condition. Prevalence, on the other hand, counts all existing cases—both new and pre-existing—at a specific point in time (point prevalence) or over a defined period (period prevalence). So the correct statement is that incidence measures new cases over time, while prevalence measures all existing cases at a point or over a period. The other descriptions mix up what each rate counts—for example, incidence is not about all existing cases, and prevalence is not limited to only new cases.

Understanding the difference between incidence and prevalence starts with what each measure counts. Incidence looks at new cases that appear in a population during a defined time period, giving a sense of the rate at which people are developing the condition. Prevalence, on the other hand, counts all existing cases—both new and pre-existing—at a specific point in time (point prevalence) or over a defined period (period prevalence).

So the correct statement is that incidence measures new cases over time, while prevalence measures all existing cases at a point or over a period. The other descriptions mix up what each rate counts—for example, incidence is not about all existing cases, and prevalence is not limited to only new cases.