Not if they were tested with PCR. PCR can have false negative, but false positive is extremely unlikely.

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.

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

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