This is a problem with the PCR tests we are using. We are multiplying (by The PCR cycles) molecules from the coronavirus. So, small parts and we don't know if the virus was dead or alive, or even if it was SARS-CoV-2 or just the common cold coronavirus. We have posted about the before.

https://theminnesotasun.com/2020/09/19/growing-research-indicates-many-covid-19-cases-might-not-be-infectious-at-all/