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': 'H5N1 is a strain of - \nSelect and explain. \nA. Avian flu, B. New vaccine against AIDS, C. Agent for japanese encephalitis, D. Causes chickengunya fever', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Avian influenza\n\nIn 1997, human cases of influenza caused by avian influenza viruses 64/1/5N) were detected in Hongkong during an extensive outbreak of influenza in poultry.\nAll these cases were associated with contact with infected poultry.\nEfficient person to person transmission has not been observed to date.\nMortality rates have been high (60%) and clinical manifestations have differed somewhat from those associated with typical outbreaks of influenza.\nTransmission of avian influenza A/H7N7 viruses from infected poultry to humans has been observed in the Netherlands, resulting predominantly in cases of conjunctivitis and some respiratory illness.\nInfection with A/H9N2 viruses along with mild respiratory illness has been reported in children in Hongkong.\nBecause of the absence of widespread immunity to H5, H7 and H9 viruses, concern has been raised that avian-to-human transmission may be the basic for the emergence of pandemic strains.', 'role': 'assistant'}]