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
The infectivity of chickenpox lasts for 
Select and explain. 
A. 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
B: 6 days after onset of rash
Answer: B: 6 days after onset of rash 
Explanation: Period of communicability:
– Chickenpox: 1 – 2 days before to 4 – 5 days after appearance of rash
– Measles: 4 days before to 5 days after appearance of rash
– Diphtheria: 14 – 28 days from disease onset
– Poliomyelitis: 7 – 10 days before and after onset of symptoms