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
Infectivity period of chickenpox is: March 2009 
Select and explain. 
A. 1 day before and 4 days after appearance of rash, B. 4 days before and 1 day after appearance of rash, C. Only when scab falls, D. Entire incubation period
A: 1 day before and 4 days after appearance of rash
Answer: A: 1 day before and 4 days after appearance of rash 
Explanation: Ans. A: 1 day before and 4 days after appearance of rash Chickenpox/ varicella is a highly infectious disease that spreads from person to person by direct contact or by air from an infected person's coughing or sneezing. Touching the fluid blister can also spread the disease. A person with chickenpox is infectious from 1-2 days before the rash appears. The contagious period continues until all blisters have formed scabs, which is about 4 to 5 days after the rash. After the spots have scabbed over, the sufferer is still highly contagious, from 10 to 21 days, meaning they can still spread the virus through close contact, breathing, and even sleeping in someone's bed. It takes from 10 to 21 days after contact with an infected person for someone to develop chickenpox.