Roseola (roseola infantum) is a mild viral illness affecting young children. When a child has roseola, he or she has a sudden high fever followed by a rosy-pink rash appearing mostly on the torso, neck, and arms.

Fever seizures may occur with the illness because of the rapid increase in a child's temperature. The fever may last 2 to 3 days. As a child's temperature gradually drops, the rash usually forms and lasts 1 to 2 days.

Roseola is contagious and is most common in children 6 months to 2 years of age. It is rare after age 4.