This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Which of the following increases the prevalence of the disease- 
Select and explain. 
A. Immigration of healthy people, B. Increase in cure rates, C. Decrease in the number of new cases, D. Increase in duration of disease
D: Increase in duration of disease
Answer: D: Increase in duration of disease 
Explanation: Ans. is 'd' i.e. Increase in duration of disease Prevalence refers "to all current cases (old + new) existing at a given point in time (point prevalence) or over a period of time (period prevalence) in a given population"It thus includes all the new cases, as well as those old persisting cases.