Which statement best defines incidence?

Which statement best defines incidence?

• A. The proportion of a population with disease at a given time.
• B. The total number of existing cases.
• C. The occurrence of new cases during a period.
• D. The average duration of disease.

Answer: (C)

Incidence captures new disease events occurring in a population over a defined period. It measures the flow of new cases, reflecting the risk of developing the disease during that time. This is different from prevalence, which is the proportion of people who have the disease at a given moment, not when it began. It’s also not about the total number of existing cases in absolute terms. So, describing incidence as the occurrence of new cases during a period best reflects its meaning. Incidence can be expressed as a cumulative proportion or as a rate per person-time.

Incidence captures new disease events occurring in a population over a defined period. It measures the flow of new cases, reflecting the risk of developing the disease during that time. This is different from prevalence, which is the proportion of people who have the disease at a given moment, not when it began. It’s also not about the total number of existing cases in absolute terms. So, describing incidence as the occurrence of new cases during a period best reflects its meaning. Incidence can be expressed as a cumulative proportion or as a rate per person-time.