Chronic Fatigue Syndrome Support Group
Chronic Fatigue Syndrome (ME/CFS) describes a sense of exhaustion and post-exertion malaise, even when you have gotten enough rest and sleep. The disease is characterized by six months of incapacitating fatigue experienced as profound exhaustion and extremely poor stamina, and problems with concentration and short-term memory. The cause is unknown, but it is a...
http://en.wikipedia.org/wiki/Cytomegalovirus
Epstein-Barr falls into this category apparantly !
Sorry I can't give you a great insight or wisdom into this but am sure others that come here regularly will be able to translate it into a more simplified form.