The leader of the expedition gave me a list of things to get for the adventure. One of the items was "Get a water stick do you do not get "Beaver Fever." What? Beaver Fever?? Of course, I laughed for obvious reason...until get explained what beaver fever. Then, it wasn't so funny.
Beaver fever is an intestinal infection caused by a microscopic parasite known as Giardia lamblia. It is caused by ingesting water cantaminted by animals (beavers) that live in or near water and poop in it.
To prevent contracting this parasite, it is important to use a "water stick" that filters 99.9999% of all ickies one might get from drinking water in the wild.