This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'True about varicella is following except: \nSelect and explain. \nA. One stage of rash is seen at one time, B. Humans are the only known reservoir, C. Children between 5 - 10 years old are most commonly affected, D. Patients are infectious - 48 hours before onset of the vesicular rash and until all vesicles are crusted', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., One stage of rash is seen at one time (Ref: David Greenwood, 18th/e, p. 428)* The skin lesions of chickenpox VZV - the hallmark of the infection - include maculopapular, vesicles, and scabs in various stages of evolution. These lesions, which evolve from maculopapular to vesicles over hours to days, appear on the trunk and face and rapidly spread to involve other areas of the body. Most are small and have an erythematous base with a diameter of 5-10mm. Successive crops appear over a 2 - to 4 - day period.", 'role': 'assistant'}]