An estimated three in 1,000 people suffers from the mysterious affliction chronic fatigue syndrome. Those people were probably enthusiastic in October when a team of U.S. medical researchers released a study arguing that not only is the syndrome real (some doctors dismissed it as purely psychological “yuppie flu”), but also that they’d connected it to a specific virus. DISCOVER covered the hubbub after the paper came out in the journal Science.

But now, in a study in PLoS One, a British research team has cast doubt on the American team’s findings, saying there’s no conclusive link between the virus and chronic fatigue syndrome, which is also known as myalgic encephalomyelitis.

The U.S. team’s findings sounded robust when they came out. They found the murine leukaemia virus-related virus (XMRV) in blood samples of 68 of 101 patients diagnosed with chronic fatigue syndrome. Just eight out of 101 healthy “controls” drawn at random from the same parts of the US also tested positive, suggesting that XMRV played a key role in triggering the condition [The Independent]. When the scientists from Imperial and Kings colleges in London attempted to replicate these findings, however, they found nothing of the sort. Of the 186 people with the syndrome that this team tested, not one showed signs of XMRV, or of any related virus.

Study coauthor Myra McClure of the Imperial College also criticized the U.S. team and the journal Science for rushing the findings into print in October. “When you’ve got such a stunning result you want to be absolutely clear that you are 1,000 per cent right and there are things in that [previous study] I would not have done. I would have waited. I would have stalled a little” [The Independent], she said.

As for the new study conducted in London, McClure declared: “We used very sensitive testing methods to look for the virus. If it had been there, we would have found it…. We are confident our results show there is no link between XMRV and CFS, at least in the UK” [The Guardian]. But the U.K. team says its contradictory findings could have resulted from differences in patients. According to the new study, the discrepancy “may be a result of population differences between North America and Europe regarding the general prevalence of XMRV infection, and might also explain the fact that two US groups found XMRV in prostate cancer tissue, while two European studies did not.”

Though McClure and her colleagues can’t say for sure how they and the Americans came to such different results, they wanted to put a stop to the rush of patients who started seeking antiretroviral treatments for chronic fatigue after the Science paper came out in October (XMRV is a retrovirus, like HIV). They say potent antiretroviral drugs should not be used to treat CFS because there is not enough evidence that this is necessary or helpful. The drugs may do more harm than good, they say [BBC News].

This might throw a wrench into the plans of Judy A. Mikovits, the lead author of the U.S. paper, to go ahead with antiretroviral testing. But the “avalanche of subsequent studies” that one medical researcher predicted to The New York Times after Mikovits’ paper is sure to continue.

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Image: Whittemore Peterson Institute