system
Given the following post, respond as if you're commenting on Reddit:
human
How does waste water testing identify specific viruses based on protein fragments, especially after hours or days of degradation?

I'm having a very hard time establishing exactly what technology is used for waste water testing for viral fragments, most fact sheets just say things like

>The samples are analysed for viral fragments

Which while perfectly fine as a public service announcement, leaves me craving a jucier explanation.

What tests are actually performed and how accurate are they?  Is the same technology used elsewhere or for other reasons? (eg: could it detect proteins that could, for example, indicate areas with relatively good or poor nutrition?)
gpt
It's a PCR test.  The actual magic of a PCR test is the PCR part isn't actually the test. The PCR part is a trick we found where you can take basically anything, Mix it with some chemicals and free DNA bits and then heat and cool it a bunch and you'll end up with a billion copies of every single bit of DNA that was in the thing in a big bucket.   


Then you do the actual test, which is thinking of a sequence of DNA you are sure is only in the thing you are looking for then you make a chemical that can stick to that sequence and react and you make a jar of that. Then you pour the jar into the bucket and if it turns red then it found the DNA and if it didn't the DNA wasn't there.   


It's really extremely accurate, it can fail for sure, but the steps it failed you KNOW it failed, if you don't end up with a bucket of DNA then you did it wrong and have to try again, if the reaction happens then you know it really stuck to that specific sequence of DNA, and you know that there was some of that creature in it, and since it multiply the DNA a bajillion times you know it'll find it even if there was only a teeny tiny amount.