Roseola infantum, also known as roseola, is characterized mainly by a fever lasting three to four days followed by the appearance of a rash as the fever subsides. This viral infection is caused by human herpesvirus types 6 and 7. Roseola is not measles, although both conditions involve a high fever followed by a rash. However, during the rash phase of measles, the fever continues to rise, accompanied by other respiratory symptoms. Consequently, the fever in measles lasts much longer compared to roseola, where the rash appears after the fever subsides. The presentation of the rash in roseola is distinctly different from that of measles, hence roseola is not referred to as measles. However, roseola is sometimes known by another name, German measles, which should not be confused with regular measles. The name "German measles" stems from the similarity of the rash in roseola to that of measles.