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': 'The 1997 bird flu pandemic was caused by which of the following strain? \nSelect and explain. \nA. H1N1, B. H5N1, C. H2N1, D. H4N1', 'role': 'user'}, {'content': "Answer: B \nExplanation: Human infections with an influenza H5N1 was first repoed in Hong Kong in 1997. Ref: Epidemiology of communicable diseases Park's textbook of Preventive and Social Medicine, 21stedition, page-330.", 'role': 'assistant'}]