Sadly PCR tests for COVID also test positive for flu and half a dozen other causes. That's why CDC/FDA are seeking proposals for a new test that actually works!
https://www.cdc.gov/csels/dls/locs/2021/07-21-2021-lab-alert...
https://www.cdc.gov/csels/dls/locs/2021/07-21-2021-lab-alert...
https://www.reuters.com/article/factcheck-covid19-pcr-test-i...