Roseola infantum commonly occurs in infants under one year old, caused by human herpesvirus type 6 infection. It typically presents with very high fever, with temperatures often reaching 39-40 degrees Celsius, and throat congestion. However, the patient generally remains in good condition without obvious symptoms of infection or poisoning. Blood tests are generally normal, indicating a viral infection. Symptomatic treatment is given, and about three to five days later, the temperature abruptly drops. One to two days after the temperature returns to normal, a red, rose-like rash appears, primarily on the head, face, and trunk, consistent with the clinical manifestations of rash following the resolution of the fever.