The 1997 bird flu pandemic was caused by which of the following strain?: (A) H1N1, (B) H5N1, (C) H2N1, (D) H4N1
Answer is B. 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.