Researchers have rejected the link between chronic fatigue syndrome and the XMRV virus as the disease’s cause.

Scientists are refuting a 2009 study that claimed XMRV was the cause of chronic fatigue. It means that donated blood no longer needs to be screened for XMRV.

The virus led to theories that samples of blood taken from CFS (chronic fatigue syndrome) patients may be the cause of the disease - spreading via transfusion.

"The original findings that led to the concern and the excitement that this is real aren’t reproducible," says Michael P. Busch, MD, PhD, professor of laboratory medicine at the University of California at San Francisco and director of the Blood Systems Research Institute.

"I take that as an indication that those results are unreliable," Busch said.

An age-old disease, chronic fatigue first cropped up in Los Angeles, seventy seven years ago, then referred to as atypical poliomyelitis.

Symptoms of malaise, poor unrefreshed sleep and widespread muscle and joint pain, occurred in doctors and nurses from the Los Angeles County Hospital.

Further reports in 1950s led to the classification of it as benign myalgic encephalomyelitis (ME), due to its muscular pain - myalgia and inflammatory links to the Central Nervous System (encephalopathy).

XMRV was discovered in 2006, but has not been found in a large number of studies with chronic fatigue since then.

The new study published Thursday and based on the findings of researchers at nine different laboratories, including the authors of the original report that linked XMRV with chronic fatigue and found that the lab tests used to detect the retrovirus were unreliable.

The laboratories have now analyzed blood samples from 15 individuals which were XMRV-infected, and found that the virus was not actually present in tests.

Additionally some of the original study researchers were now retracting their results after finding evidence of contamination.