Back pain following a fever may result from muscle strain due to prolonged bed rest, viral infections, or, less commonly, a kidney or spinal infection. Mild cases often improve with rest, gentle stretching, warm compresses, staying well-hydrated, and taking over-the-counter pain relievers such as paracetamol. However, you should see a doctor immediately if the pain is severe, persistent, or accompanied by unusual symptoms, as these may indicate a serious medical condition requiring prompt treatment.