Featured: July 21, 2010 - On July 1, 2010, CDC researchers and colleagues from two institutions reported results of a study in which they found no evidence of infection with xenotropic murine leukemia virus-related virus (XMRV) among patients with chronic fatigue syndrome (CFS), a serious disorder that affects 1 to 4 million U.S. adults. The CDC-led team used a combination of different molecular and serologic assays to test archived blood specimens from CFS patients and healthy controls. Results of blinded testing performed at CDC and two other laboratories were negative for XMRV. These findings are in sharp contrast to results from a recent U.S. study by Lombardi et al (Science 2009) that detected XMRV in about two-thirds of CFS patients and nearly 4% of healthy controls, but are consistent with three other recent studies in Europe that found no link between XMRV and CFS. The CDC-led team concluded that these data do not support an association between XMRV and CFS in their study population.