What is the difference between incidence and prevalence?

The distinction between incidence and prevalence is crucial in epidemiology and public health. Incidence refers specifically to the number of new cases of a disease that occur within a defined time period in a specified population. This measurement helps in understanding the risk of contracting the disease and is often expressed as a rate or fraction (new cases per population at risk).

Prevalence, on the other hand, indicates the total number of existing cases of a disease within a population at a particular point in time. It includes both new and prior cases, providing a snapshot of the disease burden within the population at that moment. Prevalence can be described as a point prevalence or period prevalence, depending on whether it is measured at a specific time or over a time period.

Understanding these definitions helps in interpreting data when assessing public health responses and resources. Option C accurately captures this by stating that incidence measures new cases over a specific period, while prevalence measures all existing cases at a specific point in time.