Myalgia is a term used to describe muscle pain, which can be caused by a number of conditions or diseases. Overuse, viral or bacterial infections are common causes of muscle aches. Autoimmune diseases, such as lupus or fibromylagia, can also manifest themselves in chronic muscle pain and widespread aches. You can find more information here:
. http://www.nlm.nih.gov/medlineplus/ency/article/003178.htm#Definition
