Chronic fatigue syndrome is a medical condition so vague that there were serious scientists arguing for more than a decade that it did not really exist. Most of that vagueness is about to disappear because of the discovery described in Scientific American:
A virus, which had been known to scientists for a few years, was found in chronic fatigue syndrome patients. The researchers found the XMRV virus, which had previously been linked to forms of cancer, in 2/3 of patients with a chronic fatigue syndrome diagnosis, but in only 1/27 of other people. Finding this virus will give scientists a place to start to understand the mechanisms of chronic fatigue syndrome. After the cause is understood, the disease will probably be renamed to distinguish the majority of cases that are related to this virus, along with possibly other viruses that have similar effects, from the smaller number of cases that still have no known cause.
Lyme disease was originally misdiagnosed as chronic fatigue syndrome. Then scientists identified the bacteria that causes Lyme disease, and that discovery clearly separated Lyme disease from chronic fatigue syndrome, and the treatment for Lyme disease quickly came into focus. In the next three years, I expect we will see the same thing happen for the majority of cases of chronic fatigue syndrome.