Yeah, that's what I've read. I was mostly handling water in well-travelled wilderness in the Appalachians and Rockies, though. And from what I understand there's enough of a disease load in say, the deer population in the Sierras, that you might not want to be doing it even if you don't think there's humans upstream. shrug Wasn't a huge amount of trouble, my brother has a pretty high-end pump filter.