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': 'Criteria for defining polio epidemic are all except:(2004) \nSelect and explain. \nA. 2 or more cases, B. Cases should occur in the same locality, C. Caused by the same virus type, D. Cases occurring during the 6 month period', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans: dRef: Park, 17th ed, p. 157 & 18th ed, p. 166', 'role': 'assistant'}]