“Question: How certain are we that the “COVID-19” test only shows a positive for COVID-19?”
RNA is composed of repeating units of “Letters,” which are partial chunks of protein that repeat, not in a steady pattern. Each letter is a fairly long molecule by itself. SARS2-CoV is the virus, the RNA strand in it is composed of around 30,000 letters. The PCR would take days to exactly match it, if it could at all, so they just scan for chunks of it, called the “Target Sequence.” Each target sequence is around 2,000 letters long, iirc.
The test scans for 2 different target sequences. Different countries use different target sequences. You must hit both to be a “positive.”
There is overlap with other coronaviruses for the sequences, yes. A single hit would not be definitive. Hitting both is supposed to be exclusive, but from what I understand, it is not. I believe you can have 2 other coronaviruses and set off the PCR positive, without actually having SARS2-COV. How often this happens, I do not know.
That’s the extent of my knowledge.
Thanks for the explanation