Measles, rubella and congenital rubella — branching viva

Opening question

Examiner: Take me through this child. What is the most likely diagnosis, and what is your frame for managing it? ^[5]

Candidate: The most likely diagnosis is measles. The combination of fever, the 3 C's — cough, coryza, conjunctivitis — Koplik spots on the buccal mucosa, and a cephalocaudal maculopapular rash in an unvaccinated child with an exposure history is classic. My frame is two-layered: support this child now, and run the public-health response to stop transmission to other susceptible contacts — particularly pregnant women, infants and immunocompromised people. I would isolate immediately, confirm with IgM and PCR, give vitamin A, provide supportive care, and notify public health on suspicion. ^{[5] [1]}

Examiner: Why isolate before you have confirmation? ^[1]

Candidate: Because measles is one of the most contagious infections in medicine — up to twelve to eighteen secondary cases per case in a susceptible population — and the child is most infectious in the prodrome, before the rash appears. Waiting for laboratory confirmation before isolating allows the exact transmission we are trying to prevent, so we isolate on suspicion with airborne precautions and notify simultaneously. ^{[1] [5]}