When the body temperature is greater than 37.2 degrees, it is called fever. Acute fever is defined as a fever lasting less than 2 weeks; chronic fever is defined as a fever lasting more than 2 weeks. The common causes of acute fever are cold, pneumonia, etc. Ideas for diagnosing diseases: fever + other symptoms = symptom-related diseases, e.g., fever + diarrhea = enteritis; fever + painful urination = urinary tract infection; fever + jaundice = infection of the hepatobiliary system; fever + abdominal pain = acute abdomen; fever + cough = pneumonia. Chronic fever is more difficult to diagnose. A fever greater than 2 weeks and without accompanying symptoms is often called a fever with a cause to be investigated. Hospitalization is required for careful investigation.