Ruth, come on, you don't know it . At this moment nobody really knows something for sure, i think. HTLV (Ruscetti) and Hepatitis C (Alter) were not contaminants either. That does not prove anything about XMRV of course, but these people are no beginners. We are voting in the Vivint contest and donating to the WPI so they can hopefully afford any type of equipment they need. But if i see how other groups fail to find XMRV i think the WPI might have made the right choices as far as the methodology is concerned. I'm also worried about contamination, but i think they can rule this out without having to change the PCR method, by studying blinded samples that were collected and handled in exactly the same way.