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': 'The infectivity of chicken pox lasts for - \nSelect and explain. \nA. Till the last scab falls off, B. 6 days after onset of rash, C. 3 days after onset of rash, D. Till the fever subsides', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Chicken pox\n\nCausative agent → Varicella zoster virus (Herpes simplex type III).\nPortal of entry → Respiratory tract or conjunctiva\nI. P. → 10-21 days.\nInfectious period → 2 days before and 5 days after the onset of rash.\nSecondary attack rate is high → 90 %\nAge group → 5-9 Yrs.\nC/Fs - has two stages\n\n1. Pre-eruptive stage\n\nfever, back pain, malaise, shivering\n\n2.Eruptive stage\n\nRash is symmetrical, mostly on flexor surface.\nCentripetal in distribution\nMainly On trunk, less common on arms and leg\nPalms and soles are not usually affected\nThere is rapid evolution of rash\nRash is plemorphic, that is, all stages of rash (Papule, vesicle and crusts) may be seen simultaneously.\nDisease is more severe in adults than in children.', 'role': 'assistant'}]