Fevers are a symptom of an infection that can lead to uncomfortable symptoms like body aches, chills, fatigue, loss of appetite, and more. A fever is an immune response that your body activates in response to an infection. Fevers raise your body temperature to kill off the pathogens that are making you sick. However, having a fever that lasts longer than 24 hours or is over 105℉ can pose a risk to your health in ...