American research showing a link between a mouse leukaemia retrovirus (XMRV) and chronic fatigue syndrome (CFS) has not been replicated in a UK study. The study by scientists at Imperial College London and Kings College London studied 186 UK CFS patients and found no cases of infection with XMRV (Xenotropic Murine Leukaemia Virus (MLV)-Related Virus). CFS, formally known as ME, was linked to the virus by scientists in the USA who found 67% of the CFS patients they screened tested positive for XMRV.

New Scientist

Original UK study at PLoS ONE

Original US Study: Science (Subscription required)