This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'True about the epidemiology of influenza \nSelect and explain. \nA. Incubation period 10-12 hrs, B. Extra human reservoir not seen, C. Pandemics occur, D. Asymptomatic see rarely', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The incubation period is 18-72 hours.Major reservoir of influenza viruses exists in animals and birdsOccur in pandemics every 10-40 years.During pandemics, attack rates tend to be high 5-10% in adults, 20-30% in children.Infects all ages and sexes. Park 23e pg: 147', 'role': 'assistant'}]