This abstract mentions there are now SIX strains of XMRV identified...... 'Xenotropic Murine Leukemia Virus-Related Virus in Chronic Fatigue Syndrome and Prostate Cancer' James N. Baraniuk Curr Allergy Asthma Rep DOI 10.1007/s11882-010-0106-2 http://www.springerlink.com/content/416lq773u356024x/?p=564983864c6a4af683c2f38786162c61&pi=0 Abstract Xenotropic murine leukemia virus-related virus (XMRV) is a γ retrovirus that has been associated with chronic fatigue syndrome (CFS) and prostate cancer. The search for viral causes of these syndromes was reignited by the finding that RNase L activity was low in hereditary prostate cancer and some CFS patients. The six strains of XMRV that have been sequenced have greater than 99% identity, indicating a new human infection rather than laboratory contamination. DNA, RNA, and proteins from XMRV have been detected in 50% to 67% of CFS patients and in about 3.7% of healthy controls. XMRV infections could be transmitted to permissive cell lines from CFS plasma, suggesting the potential for communicable and blood-borne spread of the virus and potentially CFS. This troubling concept is currently under intense evaluation. The most important steps now are to independently confirm the initial findings; develop reliable assays of biomarkers; and to move on to investigations of XMRV pathophysiology and treatment in CFS, prostate cancer, and potentially other virus-related syndromes, if they exist.