What is childhood exanthema? Toddler exanthema, also called the sixth disease, is a common infectious disease that mostly occurs in children under 2 years old. Because its symptoms are similar to other infectious diseases, such as measles, rubella, etc., it is easily misdiagnosed. The disease is mainly caused by human herpesvirus 6 (HHV-6) and human herpesvirus 7. The spread of acute rash in young children