That all said, the Government decided to call a person a ‘case’ if their swab sample was positive for viral RNA, which is what is measured in PCR. A person’s sample can be positive if they have the virus, and so it should. They can also be positive if they’ve had the virus some weeks or months ago and recovered. It’s faintly possible that high loads of related, but different coronaviruses, which can cause some of the common colds we get, might also react in the PCR test, though it’s unclear to me if it does.

https://www.algora.com/Algora_blog/2020/10/04/german-corona-investigative-committee

https://www.globalresearch.ca/lies-damned-lies-health-statistics-deadly-danger-false-positives/5724417