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: Microbiology
[{'content': 'Infectivity of chickenpox 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: Ans. (b) 6 days after onset of rash "Period of communicability of varicella range from 1 to 2 days before the appreance of rash, and 4 to 5 days there after." The patient ceases to be infectious once the lesions have crusted. Scabs are not infective So, option "a" is wrong. Impoant features of chickenpox Causative agent - Varicella zoster virus (HHV type 3) Incubation period - 14 to 16 days Secondary attack rate - 90% Rash Chickenpox Smallpox Superfici Deep seated Pleomorphi Only one stage of rash at 1 time Centripet Centrifugal Unilocular Multilocular Dew drop like appearance Umbilicated Inflammation (+)nt No area of inflammation around vesicle Mostly flexor surface Mostly extensor surface', 'role': 'assistant'}]