Giardiasis (beaver fever)
Reviewed: March 2026
Giardiasis is an intestinal (bowel) illness caused by a tiny parasite called Giardia. It is a common illness that causes diarrhea (loose stool/poop). The most common way people get sick with giardiasis is by swallowing contaminated water, but people can also get sick from contaminated food, surfaces, and objects.
