as far as I know - but, may I suggest you research it -
looking at CV in drain water etc -------- AND, a lot of other things -- gives one of the best early warnings of outbreak areas
why? --- I'm not certain - but, I assume it's because of the catchment areas and the fact that you catch all ---------- like every bum on every seat ends up in places where you can trap 'evidence' --
whereas say - individual testing - you only get the ones you test - and, even with random testing - you are looking at a teeny percentage of those same bums on seats every day - so, you can easily miss with individual testing - but, you easily see areas where outbreaks are about to happen and have already begun
something like that
when you spot the evidence in the dunny water - you go out to those areas and hit them hard (or harder) with the individual tests.
