Congratulations on completely misunderstanding my post! Anyway as I pointed out Dr Singh explains this very well She also explains why the nested PCR at the WPI is probably contaminated, using the wrong methodology. Contamination of PCR is very common, by it's nature it's very easy to contaminate, I'm not really sure what you're complaining about. Recombinant retroviruses are a worry as I've already said but if the WPI findings are the result of contamination, as seems increasing likely then it means that XMRV infection is not correlated with ME. That's what I meant by does it matter where the contamination came from.