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 can cause an increase in the prevalence of the disease- 
Select and explain. 
A. Immigration of healthy persons, B. Increased cure rate of disease, C. Longer duration of illness, D. Decrease in population
C: Longer duration of illness
Answer: C: Longer duration of illness 
Explanation: Ref: Parks 23rd edition Disease will be Prevalent so long it exist in the community. Longer the duration of the illness, longer will it persist in the community and hence higher will be its prevalence.