Roseola usually causes a high fever that lasts about three to five days. The fever can reach temperatures as high as 103 to 105 degrees. Just as the fever breaks, a rash usually forms on the trunk.

Measles IgM can usually be detectable after the first 3 days of the exanthem. In roseola, after an incubation period of 5–15 days, infected children develop high fevers that last 3–5 days.