Children with fever with no other symptoms can be seen for the following reasons: i. The most common is infection of the pharynx, and infection of the tonsils can be just fever, without symptoms such as runny nose and cough. Second, the early stage of hand, foot and mouth disease can be just fever, after one to two days hand, foot and mouth can appear herpes. Third, the main clinical manifestation of urinary system infection is fever, accompanied by mild back pain, frequent urination, urgent urination and painful urination, but the younger the child is, the poorer the expression ability, so the clinical manifestation is only fever, and no other symptoms will be described. Fourth, immune system diseases, the onset of which is relatively rare such as Kawasaki disease, are mostly seen in children between four months and three weeks of age, starting with a fever for two to three days, followed by a rash, chapped lips and other symptoms.