Derek Lowe of In the Pipeline blogs about another recent paper that reports no connection between the xenotropic murine leukemia virus-related virus and patients surveyed with chronic fatigue syndrome. Harriet Groom et al. write that, in the examination of 170 samples from CFS patients from two cohorts and 395 controls for XMRV infection, they “have not identified XMRV DNA in any samples by PCR.” These results are among several others that contradict the findings reported in an October 2009 Science paper, which suggest that the retrovirus is detected in the blood cells of patients with CFS.