I certainly don't treat cooking water! What a waste!

My concern here in the Cascades is primarily the many lakes whose inlets and outlets dry up by midsummer, so there's no circulation. We have a number of such areas, nearly all of which are named or nicknamed "mosquito," which means most of us visit only in late summer or early fall during the "no circulation" season. People swim in those (water is a bit warmer)! The other concern is rivers that drain inhabited areas (= septic fields and sewage plants and maybe a few old-fashioned privies) and/or drain agricultural areas (agricultural chemicals which can't be filtered out). I stay away from the last!

That's true for all the things EPA regulates--the manufacturers are responsible for testing and submit their results. My late ex-husband used to do field testing for a pesticide company. Lots and lots of paperwork!

The fact that someone has taken a lot of trips with no water treatment and never been sick is not proof of anything. The person may be immune (I suspect I am, having drunk from mountain streams since childhood) or lucky. Anecdotes are not data!

I have, though, found dead animals in the water upstream of where I was getting water, which has made me more cautious. I also know of one high-altitude spring in the Glacier Peak Wilderness that was the site of popular hunting camps for many many years before the Forest Service put in wilderness toilets. I suspect the ground water there may be polluted, since I know several people who got sick from it (that being the only place they didn't treat their water, and knowing that they're careful about hygiene). Again, that's anecdotes, though. We are dependent on the sanitary practices--or lack of them--of those who have come before us.

Norovirus has come to be a big concern, although the outbreaks on the AT seem to be spread via careless hygiene, rather than the water.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey