This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following can cause an increase in the prevalence of the disease - \nSelect and explain. \nA. Immigration of healthy persons, B. Increased cure rate of disease, C. Longer duration of illness, D. Decrease in population', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Derived Factors that increase Prevalence \n\nPrevalence increases with addition of diseased people (immigration)\nPrevalence increases with subtraction of healthy people (emigration)\nPrevalence increases with prolongation of life in chronic diseases\nPrevalence increases with decreased death rate amongst diseased\n\nDerived Factors that decrease Prevalence \n\nPrevalence decreases with addition of healthy people (immigration)\nPrevalence decreases with subtraction of diseased people (emigration)\nPrevalence decreases with increased cure rates\nPrevalence decreases with increased death rates\nPrevalence decreases with preventive programs such as immunization (which prevent new cases from occurring).', 'role': 'assistant'}]