Incidence is defined as which of the following statements?

• A. The number of deaths per 1000 population
• B. The number of existing cases of disease at a given time
• C. A measure of the disease or injury in the population, generally the number of new cases occurring during a specified time period
• D. The number of new cases occurring during a specific period/point in time

Answer: (C)

Incidence is about new cases developing in a population over a defined time. It measures the risk of starting to have the disease during that interval, often expressed as new cases per a standard population size per time (for example, per 100,000 people per year). This distinguishes it from prevalence, which counts all existing cases at a point in time or over a period. The statement that best captures incidence is that it refers to the number of new cases occurring during a specified time period. The other phrasing either points to existing cases or blends ideas in a way that isn’t about new cases occurring over a defined interval.