PatriciaABSantos on Nostr: That is a great point to keep in mind, but you should also consider the probability ...
That is a great point to keep in mind, but you should also consider the probability of having a false positive (which is what you described, detecting virus RNA without having infection) in this setting.
Every DNA/RNA that enters your bloodstream is degraded almost instantly (that’s why our body cells keep the DNA in the nucleus, away from the degrading enzimes). That’s what your immune system is constantly doing, it degrades everything and creates immunity.
For you to be able to identify a specific DNA/RNA strand in PCR, it has to be a huge amount of it floating around your bloodstream, and it must be released faster than your immune system can degrade it. And it has to be so many copies of that RNA/DNA that you can even detect it in other samples that aren’t blood (like the nose swab).
That only happens if you have a viral pathogen actively replicating and releasing millions of DNA/RNA copies per second (aka an active viral infection).
So this is why you don’t test positive for covid PCR after you take the vaccine (because your immune system took care of it all and the copies just aren’t enough to show up on the PCR). And that is why you don’t test positive for viral PCR right after you had contact with someone with a viral infection - you don’t have enough viral RNA/DNA in your sample, because the virus hasn’t made millions and millions of copies (yet, maybe after a couple of hours you will test positive).
You just don’t happen to have just enough covid DNA/RNA in your nose to test positive in PCR, that is not how it works (your immune system would not just ignore that and let it float around). False positive results can happen of course (nothing is set in stone). But in this setting, speccially with PCR technique, there’s almost 0 chance that happens. So much so the most common errors with PCR are the false negatives, not the false positives.
PCR is the most reliable and accurate test we have for viral infections.
Every DNA/RNA that enters your bloodstream is degraded almost instantly (that’s why our body cells keep the DNA in the nucleus, away from the degrading enzimes). That’s what your immune system is constantly doing, it degrades everything and creates immunity.
For you to be able to identify a specific DNA/RNA strand in PCR, it has to be a huge amount of it floating around your bloodstream, and it must be released faster than your immune system can degrade it. And it has to be so many copies of that RNA/DNA that you can even detect it in other samples that aren’t blood (like the nose swab).
That only happens if you have a viral pathogen actively replicating and releasing millions of DNA/RNA copies per second (aka an active viral infection).
So this is why you don’t test positive for covid PCR after you take the vaccine (because your immune system took care of it all and the copies just aren’t enough to show up on the PCR). And that is why you don’t test positive for viral PCR right after you had contact with someone with a viral infection - you don’t have enough viral RNA/DNA in your sample, because the virus hasn’t made millions and millions of copies (yet, maybe after a couple of hours you will test positive).
You just don’t happen to have just enough covid DNA/RNA in your nose to test positive in PCR, that is not how it works (your immune system would not just ignore that and let it float around). False positive results can happen of course (nothing is set in stone). But in this setting, speccially with PCR technique, there’s almost 0 chance that happens. So much so the most common errors with PCR are the false negatives, not the false positives.
PCR is the most reliable and accurate test we have for viral infections.