Dashing the hopes of many people with chronic fatigue syndrome, an eagerly awaited study coordinated by government health agencies has not confirmed a link between the illness and a virus called XMRV or others from the same class of mouse leukemia viruses. Two research groups had earlier reported an association between chronic fatigue syndrome and the group of viruses, known as murine leukemia viruses, or M.L.V.’s, raising hopes that a treatment or cure could be found. But later studies did not substantiate the link, and many researchers suggested that that the initial findings were the result of contamination of laboratory samples or equipment....Vincent Racaniello, a microbiology professor at Columbia University who has covered the controversy on his popular virology blog, said the XMRV/M.L.V. hypothesis was now dead....An estimated one million Americans suffer from chronic fatigue syndrome. Countless studies have documented immunological, neurological and other physiological abnormalities. Despite the name of the illness, patients have long reported that simple fatigue is not their cardinal symptom but rather what researchers call postexertional exhaustion — a profound depletion of energy after even minimal exercise or activity. Recently, a panel of top researchers proposed a new definition of the illness that requires the presence of postexertional exhaustion, rather than the six months of unexplained fatigue required under the standard definition. The group also recommended changing the name to myalgic encephalomyelitis , a virtually identical illness long recognized by the World Health Organization. “Internationally recognized experts have looked at the immune data and concluded that there very well may be a pathogen or pathogens involved in the persistence of this illness,” [a disease expert] wrote in an e-mail message.
Here's what I personally learned from this article:
There does not appear to be a link between chronic fatigue syndrome and the XMRV/MLV group of viruses.
Patients with this syndrome do not generally complain of simple fatigue but rather postexertional exhaustion.
The chronic fatigue syndrome is now considered to be identical to a long-recognized disease called myalgic encephalomyelitis.
The irony about the XMRV "red herring" for chronic fatigue syndrome is that it seems to have opened up more serious inquiries about the viral etiology of the disease, resulting in a merger with another disease, myalgic encephalomyelitis (ME). Here is a brief summary about the causality of ME:
Although risk factors for myalgic encephalomyelitis have been identified, no single definitive virus has been found in all cases, which has lead to the claim that ME is a common end path of a variety of infectious insults, perhaps most commonly in the retroviral family. It is still possible ME involves some combination of both environmental and genetic factors....Although most accept an infectious explanation, several theories suggest that ME is an inappropriate immune response to an underlying condition, a theory bolstered by the observation that there is sometimes a family history of autoimmune disease. There is also a shift from the Th1 type of helper T-cells, which fight infection, to the Th2 type, which are more active in allergy and more likely to attack the body.