This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
The recent an flu outbreak is caused by which of the following strain 
Select and explain. 
A. H1N1, B. H5N1, C. H7N9, D. H7N7
B: H5N1
Answer: B: H5N1 
Explanation: H5 N1 is the most common an flu strain that has been endemic in the world for the past 15 years origin It was first repoed from hong kong in 1997 and has spread to various countries including India Transmission Transmission to man occurs only from birds , and requires close respiratory contact clinical feature H5N1 an flu strains are associated with higher rates of pneumonia and extra pulmonary manifestations such as diarrhoea and CNS involvement Ref: Essentials of Medical microbiology apurba sastry 1st edition page 462