Which measure reflects the total number of existing cases of an illness at a given time, whether new or longstanding?

• A. Incidence
• B. Mortality rate
• C. Prevalence
• D. Morbidity

Answer: (C)

Prevalence captures how widespread a disease is at a specific moment by counting all people who currently have the illness, including both long-standing and newly diagnosed cases. This reflects the overall burden in the population at that time. Incidence, in contrast, is about new cases that develop during a defined period rather than the total number existing at a moment. Mortality rate concerns deaths due to the disease, not how many people are living with it. Morbidity is a broader notion of illness burden and isn’t the precise count of current cases. Therefore, prevalence is the measure described.