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It’s the other way around. It’s very easy to get a false positive due to DNA contamination.

As someone also said, one of the biggest enemies of PCR is contamination, or perhaps the samples had conservation / handling problems which meant the RNA ended up degraded.

Given the (currently) very low numbers of these "apparently relapsed" cases versus the total recovered cases, I think it is most likely.

What about the symptoms?

I can think of two ideas on top of my head:

- Similar sympthoms but different disease (flu?)

- False negatives, and so people were still actually sick

In addition, I wonder if those patients had distinct clinical features compared to others. In absence of more data (and these cases are very uncommon) it is hard to tell.

Probably a good idea would be to do a study with periodical follow up of a large cohort of discharged patients. This would probably give better indication.

Globally we are running 100-thousands of tests per week, we must expect to see some false positives under these circumstances.