Children always have fever in the afternoon, blood routine and mycoplasma nucleic acid PCR is normal, can exclude mycoplasma infection, normal blood routine suggests that systemic inflammation index is not high, the possibility of bacterial infection is small, you can consider the special pathogens infections and fever caused by other diseases. May be viral, tuberculosis infection caused by fever, there may be other non-infectious diseases caused by fever. 1. Tuberculosis infection: children often have afternoon low-grade fever, night sweats, if tuberculosis, may be accompanied by coughing, coughing up sputum and other respiratory symptoms, through the tuberculin test, sputum smear, culture and other tests can help diagnosis. 2. Viral infections: children with viral infections may have normal blood counts or leukopenia and lymphocytosis, mostly respiratory tract infections, children may have cough, dyspnea, wheezing and other discomforts, and relevant respiratory viral pathogenetic tests can be used to help diagnose the disease. 3. Other non-infectious diseases cause fever, such as Kawasaki disease, autoimmune diseases, such as systemic lupus erythematosus, etc. Fever can also occur, often accompanied by skin rashes, mucous membrane damage, etc., according to autoantibody tests and other clinical manifestations to help diagnosis. Children with fever should actively seek medical attention to identify the cause of the disease and treat it as soon as possible.