The PCR test is overly sensitive. The virus has a ~32k DNS, the test searches for len=600 matches. If the immune system has killed the virus the remaining RNA strains in the body usually are much longer than 600 even if the virus is long killed, and torn apart. This not infective. It was found out that too many people tested positive again at the 2nd test. This was not a reinfection. The reinfection period starts after 6-12 months, as with any other common cold.
The best test for testing infectiveness is the antigen test, and then you need a 2nd PCR test for confirmation that it is SARS-COV-2 and not some other common cold variant.
The best test for testing infectiveness is the antigen test, and then you need a 2nd PCR test for confirmation that it is SARS-COV-2 and not some other common cold variant.