Doubt has been cast on recent claims that a human retrovirus known as XMRV is associated with chronic fatigue syndrome or ME (myalgic encephalitis) by a new study by researchers in Netherlands.

Contradict a recent study from the US that detected XMRV in two thirds of patients with chronic fatigue syndrome, the findings in the British Medical Journal could not conclusively prove a direct (causal) link between the virus and the disease.

In January 2010, another research team found no evidence of XMRV in 186 patients with chronic fatigue syndrome in the United Kingdom. A third study, published earlier this month, also failed to identify XMRV in 170 patients.

The authors say," 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."

One reason why these results contradict the original findings might be that the US study involved patients from a specific outbreak of chronic fatigue syndrome in the mid-80s that has already been linked to several viruses, said the researchers.

It was concluded by them that it is possible that XMRV is implicated in this outbreak, but does not play a substantial role in most cases of chronic fatigue syndrome elsewhere.(With Input from Agencies)