Fever after lumbar pain is mainly seen in infectious diseases, may be caused by the following three conditions: First, lumbar pain and accompanied by fever, may be due to lumbar bacterial infection, lumbar vertebrae blood flow rate is slower, so the bacteria are easy to stay within the vertebrae to form an infection. Once the infection is aggravated, it will inevitably lead to lumbar pain and fever symptoms. Second, lumbar pain and accompanied by fever, may also be due to lumbar tuberculosis. Although the temperature of the fever caused by tuberculosis infection is not high, but it will lead to obvious waist pain and low fever. Third, back pain and fever may also be caused by a viral infection.