The waters of the Adirondacks were safe were apparently safe for a long time, up until the 70's, when the efforts of the conservation folk got beaver populations re-established. Giardiasis, aka beaver fever, followed promptly. A friend got it because the family dug well was too close to the the creek. She was in the first trimester of pregnancy, and chose not to risk damaging the fetus with the treatment of choice; she chose instead the local herbalist's cure which involved a 24 hour fast, followed by ingestion of an entire bulb of garlic, pureed, mixed in tomato juice, followed by another 24 hour fast. She was pretty sure that she could hear the giardia screaming when the garlic hit them, and allowed that they surely were in a hurry to leave. No damage to the fetus, tho she was born Italian. Anyway, giardia is seldom fatal, mostly involves occasional abdominal cramps and diarrhea. Having it is sort of like having a pet that lives in your gi tract.