Measles outbreak in displacement camp — DTM&H MCQ

Correct answer: E — Isolation of cases with rapid measles vaccination of susceptible contacts

The correct answer is E, isolation of cases with rapid measles vaccination of susceptible contacts. The stem describes classic measles (fever, rash, cough, coryza, conjunctivitis) in an overcrowded displacement camp with unvaccinated children and infants too young for routine immunisation, the exact scenario in which measles spreads explosively because it is one of the most transmissible pathogens known, with an attack rate approaching 90 percent in susceptible close contacts. UK national guidance directs that suspected cases be isolated promptly and that susceptible contacts receive MMR vaccine as post-exposure prophylaxis, ideally within 72 hours of exposure, since this is the single intervention proven to interrupt onward transmission and protect the immunologically vulnerable infants who cannot yet be vaccinated. Rapid case isolation plus ring vaccination of contacts breaks the chain of transmission before it seeds a camp-wide epidemic, which is the dominant public health threat here, not the other differentials offered. Why the other options are wrong: B. Praziquantel mass treatment: this treats schistosomiasis, which is irrelevant to a febrile rash illness with cough, coryza and conjunctivitis, and does nothing to interrupt an airborne viral outbreak. C. No action until serology returns for every case: measles is clinically diagnosable and waiting for laboratory confirmation before acting would allow uncontrolled spread in a crowded, non-immune population; outbreak response must start on clinical suspicion. D. Container source reduction around shelters: this is a vector-control measure for mosquito-borne disease such as dengue and has no bearing on a respiratory, droplet-spread viral illness. A. Doxycycline prophylaxis for every contact: doxycycline is an antibacterial with no activity against measles virus, and is also contraindicated in young children. Key point: In a susceptible, crowded population, suspected measles demands immediate case isolation and prompt MMR vaccination of susceptible contacts rather than awaiting confirmatory testing.

Reference: UK Health Security Agency, National Measles Guidelines (2024), Section 2.2 Management of contacts and post-exposure prophylaxis, gov.uk/government/publications/national-measles-guidelines