So much for the theory that you are immune once you recover.
I wouldn't sound the alarm just yet:
Officials are still investigating the cause of the apparent relapses. But Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention (KCDC), has said the virus may have been reactivated rather than the patients being re-infected.
Other experts said faulty tests may be playing a role, or remnants of the virus may still be in patients’ systems but not be infectious or of danger to the host or others.
Yep, especially if there's something like 30% false negative rate for such tests...
https://www.livescience.com/amp/covid19-coronavirus-tests-false-negatives.html
Of course, then one wonders exactly what good such testing does under the circumstance... although repeat testing would presumably help reduce the errors, but if testing takes significant time and is also very limited in availability...
I suppose that's one significant (but not politically expedient, so largely unpublicized) reason to only do this kind of testing for those who already "pass" the "eye test" for Covid-19...
All the more reason to work toward new, better testing that could become abundantly available asap...
_Man_