Hopes of discovering treatments for chronic fatigue syndrome dimmed on Friday after a new study cast doubt on previous findings that a virus linked to prostate cancer might also be associated with the condition.
A Dutch research team investigated a possible link in a European group of patients with the fatigue disorder, also known as ME, that affects 17 million people worldwide, but found no evidence of the virus, known as XMRV.
The findings in the British Medical Journal were the latest to contradict a U.S. study published last year that found XMRV in the blood of 68 out of 101 patients with chronic fatigue syndrome (CFS).
That study prompted hopes that CFS patients might benefit from a range of drugs designed to fight AIDS, cancer and inflammation.
CFS, or myalgic encephalitis (ME), is a debilitating condition that causes disabling physical and mental fatigue that does not improve with rest.
"Although our patient group was relatively small and we cannot formally rule out a role of XMRV, our data cast doubt on the claim that this virus is associated with chronic fatigue syndrome in the majority of patients," said Frank van Kuppeveld and Jos van der Meer of the Nijmegen Medical Center, who led the study.
What causes CSF is unclear, but many people say they think their illness started after a viral infection.
No evidence of virus in patients
However, in January 2010, a British research team found no evidence of XMRV in 186 patients with chronic fatigue syndrome and a third study published this month also failed to identify the virus in 170 patients.
"Three papers from three well-respected European laboratories have now independently and unambiguously failed to find XMRV in CFS patients," said Myra McClure, a professor of retrovirology at Imperial College London.
The Dutch researchers said one reason why their results contradict the original findings may be that the U.S. study involved patients from a specific outbreak of CFS in the mid-1980s that has already been linked to several viruses.
It is possible that XMRV was implicated in this outbreak, they said, but is not linked to most cases of CFS elsewhere.
Other U.S. laboratories are now investigating XMRV and CFS further to see if any link can be confirmed.
"New results from other U.S. laboratories will now be very interesting," McClure said. "If the link fails to hold up, it will be another bitter disappointment to affected patients."
