Cryptosporidiosis results from infection with Cryptosporidium parasites. The parasite lives in the digestive tract of both humans and animals. It sheds (leaves the body) in feces (stool).
Cryptosporidium is also often found in recreational water supplies. These can include swimming pools, hot tubs, water parks, lakes, rivers, and fountains. The parasite is not killed by freezing or by the normal levels of chlorine in pools and hot tubs.
Eating or drinking contaminated water or food exposes many people to the infection. Additionally, some people contract Cryptosporidium from direct contact with another infected person.