Of the following statements, which is/are correct?
1. Incidence is the number of new cases of disease occurring in a defined population during a specified time.
2. Prevalence is the number of old cases existing at a given point in time.
3. Prevalence depends upon the incidence and duration of illness.

Correct option is D

Ans. (d) 1 and 3 only
Sol.
· Statement 1 - Correct: Incidence refers to the number of new cases of a disease occurring in a specific population within a defined time period.
· Statement 2 - Incorrect: Prevalence is the total number of cases (both new and old) present in a population at a given time, not just "old cases."
· Statement 3 - Correct: Prevalence is influenced by both incidence (new cases) and the duration of illness. If a disease lasts longer, its prevalence increases, and if it resolves quickly or leads to death, its prevalence decreases.
Conclusion:
The correct answer is (d) 1 and 3 only, as statement 2 is incorrect in defining prevalence.