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': 'Criteria for defining polio epidemic are all except ? \nSelect and explain. \nA. 2 or more cases, B. Cases should occur in same locality, C. Caused by same virus type, D. Cases occurring during 6 month period', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Cases occuring during 6 month period o An epidemic of polio is defined as 2 or more local cases caused by same virus type in any 4 week period. So, it has following features - i) 2 or more cases of polio ii) Caused by same virus type iii) Within 4 week period", 'role': 'assistant'}]