"Chronic fatigue syndrome, the debilitating condition once dismissed as "yuppie flu", has been linked to a virus that is also common in people with a certain type of prostate cancer.
It's still not clear if the virus, called XMRV, causes chronic fatigue syndrome (CFS), or is just more common in people with the disorder. But the discovery is sure to reignite the debate over whether CFS is fundamentally a psychological condition or a physiological one.
"It's a contentious area that lies somewhere between medicine and psychiatry," says Simon Wessely, a psychiatrist at King's College London who has been vilified by patient groups for his scepticism of cut-and-dried explanations for CFS and his assertion that psychological factors may play an important role."
"That sentiment is echoed by John Coffin, a virologist at Tufts University in Boston. "This looks like a very, very interesting start," he says. "It's not impossible that this could cause a disease with neurological and immunological consequences, but we don't know for sure."
Wessely points out, however, that XMRV fails to account for the wide variety of other factors associated with the CFS, including childhood trauma and other infections such as viral meningitis. "Any model that is going to be satisfactory has to explain everything, not just little bits," he says.
If XMRV does turn out to contribute to CFS, this could point to new treatments. In the UK, patients are prescribed exercise and cognitive therapy, which seems to work for some patients, but not for most. Such failings underscore the need for therapies that go after the root cause of chronic fatigue syndrome – whatever it turns out to be."