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
H5N1 is a strain of: 
Select and explain. 
A. Avian flu, B. New vaccine against AIDS, C. Agent for Japanese encephalitis, D. Causes Chikungunya fever
A: Avian flu
Answer: A: Avian flu 
Explanation: Ans. is 'a' i.e., Avian flu (Ref: Park, 22nd/e, p. 145)* At present three types of influenza viruses are circulating in the world: A(H1 N1 ),A(H3 N2 ), and B viruses.* WHO global surveillance activities have identified human infection with a new influenza virus called A(H5 N1 ),in Hong Kong in mid 1997. However, the possibility that the outbreak heralded a global influenza pandemic did not materialize and it is transmitted to man only from birds, requires close respiratory contact.