This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2018, Subject name: Microbiology
Isolation period of measles:- 
Select and explain. 
A. Onset of prodromal stage until 7th day of rash, B. Eruptive stage until 2 days of rash, C. Onset of prodromal phase until 3rd day of rash, D. Eruptive stage until 7th day of rash
C: Onset of prodromal phase until 3rd day of rash
Answer: C: Onset of prodromal phase until 3rd day of rash 
Explanation: Isolation period of measles is Onset of prodromal phase until 3rd day of rash. Maximum communicability occurs from onset of prodrome through the first 3-4 days of rash.Prodromal phase-stage last for 4 days(from 10th to 14th day of infection) characterized by Fever, Koplik spots , coryza, nasal discharge, redness .Incubation period of measles is 10 daysEruptive phase- Maculopapular rash appear after 4 days of fever (14day after infection)