This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory Infections, Subject name: Social & Preventive Medicine
Period of infectivity for chickenpox is: 
Select and explain. 
A. 5 days prior to appearance of rash till 4 days afterwards, B. 4 days prior to appearance of rash till 5 days afterwards, C. 4 days prior to appearance of rash till 1 day afterwards, D. 1 day prior to appearance of rash till 4 days afterwards
D: 1 day prior to appearance of rash till 4 days afterwards
Answer: D: 1 day prior to appearance of rash till 4 days afterwards 
Explanation: Chicken Pox Caused by HHV-3 Incubation period : 14-16 days Source of infection : Case Mode of transmission : Respiratory/ air droplets Period of communicability of Chicken pox: 1-2 days before appearance & 5 days after appearance of rash. Rash: Superficial, unilocular, Centripetal, pleomorphic rash, due drop on rose petal appearance affecting flexor aspects and axilla. Secondary attack rate : 90% Vaccine : Live attenuated vaccine : OKA strain Late complication : Shingles by recrudescence.