A 10-month-old infant has 4 days of high fever reaching 39.5 degrees C with no localizing signs. The child appears well between fever spikes. On day 4 the temperature normalizes and within hours a rose-pink macular rash appears over the trunk. What is the causative agent?
- A Human herpesvirus 6 ✓
- B Parvovirus B19
- C Coxsackievirus A16
- D Measles virus
Correct answer: A. Human herpesvirus 6
Explanation
Roseola infantum (exanthem subitum) is classically caused by human herpesvirus 6B, typically affecting infants between 6 months and 2 years. Its signature pattern is 3 to 5 days of high fever in a nontoxic child, with the rash erupting as or just after the fever falls, which distinguishes it from measles where the rash appears while fever peaks. Parvovirus B19 causes erythema infectiosum with slapped-cheek appearance, and Coxsackie A16 causes hand-foot-mouth disease.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.