The symptoms of CFS include debilitating fatigue, neurological problems, general pain, gastro-intestinal problems and a variety of flu-like symptoms.

BBC: News | Health | Immune system blamed for Chronic Fatigue Syndrome

The researchers reported they found the retrovirus XMRV in a majority of 101 patients with chronic fatigue syndrome, a debilitating condition that involves cognitive dysfunction and severe pain.

WSJ: Chronic-Fatigue Paper Called Into Question