When looking for causal factors behind health issues, it's worth it to be aware of things that are extremely common in the general population. Epstein Barr Virus is one common health threat. In fact, it is estimated that 95% of Americans have been infected by the virus by adulthood. Since we know that it is that common, the next question is, what can it cause in humans in terms of symptoms or diseases? Chronic Fatigue Syndrome is thought to be correlated to this virus, but the virus has also been correlated to Multiple Sclerosis, Lupus, Rheumatoid Arthritis and other autoimmune diseases:
A recent study published in 2012 adds more data suggesting that EBV is correlated to Chronic Fatigue Syndrome, and the authors suggest that "...even in the absence of a complete active infection, these viral proteins' ability to induce inflammatory chemical signals causes enough immune system chaos to lead to CFS." (http://www.sciencedaily.com/releases/2012/11/121114171708.htm) The difficulty in correlating the virus to CFS in the past has been that laboratory testing does not reflect an active infection. This research reflects more sensitive testing that can apparently determine when the virus is causing symptoms even in that case.