Bacterial infection leukocyte 31 fever after 3 days of injection and then fever, should be considered whether there is a mixed infection, drug fever or the presence of other disease factors, etc., should be identified to identify the causes and then adjust the treatment. 1. Mixed infection: generally refers to a mixed bacterial and viral infection, which can be treated with cephalosporin antibiotics plus oseltamivir. 2. Drug fever: refers to the fever produced by the drug itself in the course of treatment. In this case, you should strictly follow the doctor’s instructions for medication and avoid abusing drugs. 3. Fever caused by other diseases: such as autoimmune diseases (Hashimoto’s thyroiditis, rheumatoid arthritis, etc.), the treatment drugs include injections of thyroid hormone, methotrexate and so on. It is recommended that patients go to the hospital in time to clarify the type of disease and take targeted treatment. All medications should be used under the guidance of a doctor, avoid self-medication.