The symptoms of fever caused by viral infections depend on the site of the infection and the severity of the infection. When a fever is caused by a viral infection, the onset of the fever is usually rapid, with a distinct chill and high fever, usually around 39-40°C. Some patients with severe illness may also have a high fever that does not go away. In addition, when a viral cold occurs, in addition to fever, the patient may also have upper respiratory tract symptoms such as nasal congestion, runny nose, sneezing, sore throat, and occasionally a mild cough. If the upper respiratory tract infection is caused by the influenza virus, the systemic symptoms are more pronounced and usually include general malaise, weakness, poor circulation, headache, dizziness and other discomforts. Some patients with viral flu can also develop gastrointestinal symptoms, such as nausea, vomiting, abdominal pain, diarrhea, joint pain in the limbs and other discomforts. In the case of viral pneumonia, in addition to chills and high fever, patients may also have clinical symptoms such as coughing and coughing, shortness of breath, chest tightness and chest pain.