Regarding infectivity of chickenpox, a child with varicella should be considered contagious during which period?
- A From 1 to 2 days before the rash appears until all lesions have crusted ✓
- B Only while fresh vesicles continue to appear, typically days 3 to 7 of the rash
- C From onset of fever until scab separation, which may take up to 4 weeks
- D From the appearance of the first vesicle until the last vesicle ruptures
Correct answer: A. From 1 to 2 days before the rash appears until all lesions have crusted
Explanation
Varicella-zoster virus is transmissible from about 1 to 2 days before the rash appears until every lesion has crusted over, which is why exclusion from school is based on crusting rather than rash duration. Respiratory droplet spread accounts for pre-rash contagion. Crusts themselves are not infectious, so waiting for scab separation or restricting isolation only to the vesicular phase understates or overstates the true window.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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