Sorry, I could have been clearer and said something like RNA fragments (non-infectious residue of the virus). It's true that in a clinical situation, you need to treat the positive PCR as infectious until proven otherwise. But from a research standpoint, it seems possible that someone who previously had a high viral load in their lungs, and is now recovering, could have detectable Sars-Cov2 RNA fragments for a period of time despite the presence of endogenous RNAse. And they might not be contagious.