The xenotropic murine leukemia virus-related virus has nothing to do with chronic fatigue syndrome, a new study postulates but researchers have a warning for American patients.

On the repost published online on BMJ on Feb. 26, the researchers said that the study enough to give rise to doubt that XMRV is related to chronic fatigue syndrome, although the findings are not very much conclusive considering the small number of patients observed.

There is no concrete evidence of what factors cause this condition that afflicts millions of people all over the planet. A previous study, however, pointed out that two-thirds of people with chronic fatigue syndrome showed signs of XMRV.

There are a few studies that argue the finding, including this new one, saying that the virus and the condition are not related at all.

The study, which was conducted by researchers from Radboud University Nijmegen Medical Center in the Netherlands observed a total of 65 Dutch subjects, 32 of which have been diagnosed with chronic fatigue syndrome and 43 are healthy people.

They were not able to see traces of the virus in anyone in the group.

According to a commentary by researchers from Imperial College and King’s College London that was published together with the new report, the virus could be one of the causes during an outbreak of chronic fatigue syndrome in the U.S. in the 1980s.