This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Whooping Cough (Pertussis), Subject name: Social & Preventive Medicine
[{'content': 'The usual incubation period for pertusis is - \nSelect and explain. \nA. 7-14 days, B. 3-5 days, C. 21-25 days, D. Less then 3 days', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 7-14 days The incubation period of pertussis is usually 7-14 days, but not more than 3 weeks.More question on PertussisMost infectious during catarrhal stage.Infective period extends from a week after exposure to about 3 weeks after the onset of paroxysmal stage.The source of infection is a case of pertussis.There is no evidence that infection is ever subclinical a chronic carrier state does not exist.Secondary attack rate is 90% in unimmunized household contacts.", 'role': 'assistant'}]