Research finds no proof that a virus is the cause of ME

The blood samples were free of XMRV

UK scientists say they can find no proof that a particular virus is the cause of chronic fatigue syndrome (CFS) or ME, contrary to recent claims.

The Imperial College London team say they want to share the findings as some patients are pinning their hopes on drugs to fight the virus called XMRV.

They analysed blood samples from 186 patients with CFS and found none had the virus, PLoS One journal reports.

Experts said the latest findings would be a bitter disappointment to many.

They said more trials were under way and when these report in coming months, scientists will be able to draw more firm conclusions.

Work in the US, published in Science, had found the retrovirus in 68 of 101 CFS patients.

The UK team say the conflict between the two studies might be down to differences between the patients enrolled or the way the research was conducted.

Or there might be different geographical types or strains of XMRV.

Regardless, 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.

Professor Myra McClure, one of the Imperial College London investigators, said: "We are confident that our results show there is no link between XMRV and chronic fatigue syndrome, at least in the UK."

She said they had used extremely sensitive DNA testing methods, called polymerase chain reaction, to look for the virus.

"If it had been there, we would have found it."

'Disappointing'

Co-author Professor Simon Wessely said the findings did not invalidate all previous research, some of which has shown that CFS can be triggered by other infectious agents, such as Epstein Barr Virus.

The charity Action for ME said it was disappointing to hear about these findings, but said no single small-scale study could be conclusive.

Dr Charles Shepherd, of The ME Association, said it was important to remain open-minded.

"We need to be extremely cautious until we know more. There has been enormous interest in this from patients.

"Some have been led into believing the cause and a test has been discovered and that treatment is just round the corner and that is not the case.

"Over the next few weeks and months we will have more results and then we can come to a conclusion.

"If it turns out that XMRV is important, we will have to start looking at whether it is worthwhile testing for it and treating it."

In a statement, the charity Invest in ME said the original study was of the "highest quality", and that much more work was required before any firm conclusions could be drawn.