Viral infections can cause fever, but not all viral infections trigger fever in patients. Viral infections are infectious diseases in which the virus is an exogenous pyrogen. When the virus enters the body, it activates lymphocytes in the blood, causing them to produce and release endogenous pyrogens. When the endogenous pyrogen acts on the body’s thermoregulatory center, it causes the body’s temperature to rise, leading to fever. Common viruses that cause fever include influenza virus, coronavirus, hantavirus, dengue virus, herpes virus, etc. However, not all viral infections cause fever, and some viral infections cannot even be felt by the body, such as hepatitis A virus, hepatitis B virus, and hepatitis C virus. If you have symptoms of fever, you need to consult a doctor in time to clarify the cause of the disease and standardize the treatment.