Back pain after a cold may be caused by viral or bacterial infection, or it may be caused by kidney damage after a cold, or it may be caused by fever of a cold. 1. Viral or bacterial infection: Viral or bacterial infection of the human body leads to localized inflammatory reaction of the organism, so that inflammatory and toxic substances continue to be produced and accumulate in muscles, ligaments and other soft tissues, which leads to the symptom of low back pain after a cold. 2. Kidney damage: colds can easily cause kidney damage, resulting in congestion and edema of the kidneys, which can cause back pain and other symptoms. 3. Fever: colds can cause fever, when the body in order to maintain body temperature balance, need to consume a lot of energy, and energy intake is mainly in the form of anaerobic fermentation, which promotes the accumulation of lactic acid in the body, lactic acid buildup in the lower back, resulting in lumbar pain. In order to identify the cause of the disease as early as possible, it is recommended to go to a specialized hospital in time and actively cooperate with the doctor for treatment.