Only a week after a second study found no link between a mouse virus called xenotropic murine leukemia virus-related virus (XMRV) and chronic fatigue syndrome, a third study has also found no link, dashing the hopes of CFS victims that a treatment for the mysterious disease might be on the horizon.
Their hopes had been raised last October when Nevada researchers reported in the journal Science that they found XMRV in two-thirds of the CFS patients they tested, a strong indication that the virus might be involved in causing the disease -- whose origin has been so mysterious that some physicians refuse to even believe that it is a real malady. But two British research teams independently reported in the last two months that they could not find the virus in patients from that country. Now, a team from the Nijmegen Medical Center in the Netherlands reports in BMJ that they could not find the virus in 32 Dutch patients or 43 healthy controls.
"Three papers from three well-respected European laboratories have now independently and unambiguously failed to find XMRV in CFS patients," wrote virologists Myra McClure and Simon Wessely of Imperial College London in an editorial accompanying the report. There has been much talk that different protocols were used in the studies, they added, but those technical differences "are irrelevant" as long as the researchers showed that they can properly amplify the genes they are searching for.
[Updated March 1: The post wrongly said that Simon Wesseley is a virologist at Imperial College London. He is a psychiatrist at King's College London.]
McClure and Wessely speculated that there are two possible explanations for the European failures to duplicate the American findings. The most likely is that XMRV infection is geographically confined to the United States and is not a cause of CFS. A second possibility is that the U.S. patients, who were generally older than those in Europe, were linked to a specific outbreak of CFS in the mid-1980s that has been tentatively linked to several viruses.
-- Thomas H. Maugh II