The cause of chronic fatigue syndrome, a debilitating illness that afflicts some 17 million people worldwide, has long been a mystery, so much so that patients have been accused of malingering or having psychiatric problems. But new research indicates many sufferers are “infected with a little-known virus that may cause or at least contribute to their illness,” the New York Times reports. The paper references an article published online in the journal Science, that reports that 68 of 101 patients with the syndrome, or 67 per cent, were infected with an infectious virus, xenotropic murine leukemia virus-related virus, or XMRV. By contrast, only 3.7 per cent of 218 healthy people were infected. Dr. Judy A. Mikovits, research director at the Whittemore Peterson Institute in Reno and the lead author of the paper, cautions that they have not yet proven that the virus causes the syndrome. But she says their expectation is that the virus will turn out to be the cause, not just of chronic fatigue, but of other illnesses as well: “I think this establishes what had always been considered a psychiatric disease as an infectious disease,” she says.