Roseola is a viral illness that results in a viral exanthem.
Exanthem is another name for a rash or skin eruption. Roseola is a contagious disease that usually consists of a high fever and a rash that develops as the fever decreases. Roseola is caused by many viruses. The most common cause is the human herpesvirus-6 virus. It occurs mostly in children under the age of 3.