Headache, nausea, and low fever are seen in infectious diseases, and the common causes are as follows: First, acute sinusitis, in addition to headache, nausea, and low fever, there is nasal congestion, yellow purulent nasal discharge, weakness, and loss of appetite, etc. Most of them have a history of cold and flu. Second, acute tonsillitis, in addition to low fever, nausea and headache, there is also sore throat appears, to eat when obvious. The throat is uncomfortable and children are prone to cough and sputum, which can be improved by giving anti-inflammatory and antipyretic treatment. Third, intracranial infection is one of the more serious diseases, mostly seen in children and the elderly. Common pathogens include Mycobacterium tuberculosis and herpes simplex virus, etc. If there is no timely diagnosis and treatment, it can easily lead to coma, convulsions, and even life-threatening. Diagnosis relies on clinical symptoms, cranial CT examinations as well as lumbar puncture and cerebrospinal fluid laboratory tests.