Also called exanthema subitum, roseola infantum is an acute, benign, presumably viral infection. It usually affects infants ages 6 months to 1 year.

Roseola affects boys and girls alike. It occurs year-round but is most prevalent in spring and fall. Overt roseola,
the most common exanthem in infants younger than age 2, affects 30% of all children; inapparent roseola (febrile illness without a rash) may affect the rest.