XMRV is the name of a

An infectious virus linked to two diseases is drawing the attention of public-health officials, who are investigating the potential threat to the nation’s blood supply.
    It isn’t clear if the virus, known as XMRV, poses a danger, and public-health officials say there isn’t evidence of spreading infection. But because of concern over the potential for widespread infection and preliminary evidence that XMRV is transmitted similarly to HIV, officials are quickly trying to determine if action is needed to protect the blood supply.
    XMRV was discovered in 2006 when it was found in tumor samples from men with a rare form of familial prostate cancer. Research has also linked the virus to chronic fatigue syndrome and found it in measurable levels in the blood of healthy people. But the evidence isn’t conclusive, as several other studies failed to find XMRV in the blood of people with chronic fatigue syndrome, and it isn’t known how prevalent the virus is or whether it causes disease.