Click below to read my paper from 2001 on false positive PCR tests in HIV, the same test used to diagnose covid-19.  I wrote it in 2001 as a medical school research elective. There are some things I would write differently today.  For example, PCR estimated "viral loads" were found to have an incredibly high rate of "non-infectious" viral particles.  The most likely explanation for this is that PCR was cross reacting with other RNA that did not come from a virus.  
  false_positive_pcr_viral_loads.pdf