If the child only has fever without other symptoms, it is considered to be the early stage of infectious diseases or rheumatoid immune system diseases, in addition, it may also be the result of early blood system diseases. 1. Early stage of infectious diseases: In the early stage of infectious diseases, such as common cold, the child may only show symptoms of fever, followed by a series of other symptoms, such as coughing and loss of appetite. 2. Early stage of rheumatic immune system diseases: In the early stage of rheumatic immune system diseases such as systemic lupus erythematosus (SLE) and rheumatic fever, the child may temporarily show symptoms of fever, but other symptoms usually follow, such as zygomatic erythema with butterfly-shaped erythema in the zygomatic region following SLE, and coughing, sore throat, and erythema annulare in the rheumatic fever following SLE. 3. The early stage of blood system diseases: when suffering from acute leukemia, its early stage may only show fever, followed by chest pain, anemia and other symptoms. Children only fever without other symptoms, there may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.