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
[{'content': 'Which of the following increases the prevalence of the disease- \nSelect and explain. \nA. Immigration of healthy people, B. Increase in cure rates, C. Decrease in the number of new cases, D. Increase in duration of disease', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 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.', 'role': 'assistant'}]