To determine whether the fever is caused by a bacterial or viral infection, blood tests, C-reactive protein and calcitonin can be used. 1. Bacterial infection: The values of white blood cells and neutrophils in the blood test are usually higher than the normal values, and the C-reactive protein and calcitonin are also elevated. Fever is also accompanied by weakness and limb pain. Bacterial infections are treated with antibiotics such as amoxicillin and cefixime. 2. Viral infections: blood counts show normal or decreasing values of white blood cells, decreasing values of neutrophils, but elevated values of lymphocytes or monocytes. Different viral infections, different parts of the infection will have different fever temperatures and clinical manifestations. Viral infections are treated with antiviral drugs such as acyclovir and ganciclovir. It is recommended that patients with fever should consult a doctor in time to improve the examination, standardize the use of drugs under the guidance of the doctor, do not blindly use drugs on their own.