Koplik Spots Virus — MFDS Part 1 MCQ
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Correct answer: C — Measles virus
The correct answer is C, measles virus. Koplik spots are characteristic small white or bluish-white lesions on an erythematous base, typically affecting the buccal mucosa around the onset of the measles rash. They strongly support measles but should not be treated as independently diagnostic because other oral lesions can resemble them. Mumps virus primarily causes parotitis, while rubella typically produces a mild rash with post-auricular or suboccipital lymphadenopathy. Herpes simplex and varicella-zoster viruses more commonly cause vesicles that rupture to form painful oral ulceration rather than Koplik spots.
Reference: UK Health Security Agency. National measles guidelines, version 8, section 1.3.2: Clinical presentation of primary measles infection. July 2026. https://assets.publishing.service.gov.uk/media/66a0ce1449b9c0597fdb03a6/20240704_national-measles-guidelines-July-2024.pdf