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': 'Influenza pandemic is mainly caused by - \nSelect and explain. \nA. Type A, B. Type B, C. Type C, D. All', 'role': 'user'}, {'content': "Answer: A \nExplanation: ↵\nInfluenza \n\nInfluenza is an acute respiratory tract infection caused by influenza virus.\nThere are three viral subtypes\n\n\nType A → Causes all Pandemics and most of the epidemics\nType B → Can cause epidemics\nType C → Causes endemic infection\n\n\nThree types of influenza viruses are circulating in world → A (H1N1), A (H3 N2) and B\nA New type has been recognized → A (H5 N1)\nSource of infection → case or subclinical case\nMode of transmission → Droplet infection by respiratory route\nIncubation period →18-72 hours\n\nClinical manifestations\n\nMost infections are subclinical\nfever, headache and myalgia\nRespiratory → coughing\nThere is no virernia\n\nComplications\n\nPneumonia → M.C. by str. pneumoniae\nWorsening of COPD\nEncephalitis\nReye's Syndrome → with type B virus\nGB. Syndrome\nG I Symptoms (gastric flu)\xa0→ type B\xa0virus\n\nLaboratory diagnosis\n\nMost commonly, the diagnosis is established by the use of rapid viral tests that detect viral nucleoprotein or neuraminidase \xa0 - Harrison - 1069\nBest specimen is nasopharyngeal secretion.", 'role': 'assistant'}]