why do body aches happen
The specific cause of body aches (myalgia) are the interleukins, which are primarily produced by the macrophages. These interleukins cause pain, body aches, hypersensitivity of the nerves, etc. Some of the interleukins (such as IL-2) cause the fever seen during the flu, and probably the headaches. Since these interleukins are produced in response many different kinds of bacterial and viral infections, symptoms such as fever, myalgia, and headaches can be seen in infections by many different etiologic agents.