People acquire the infection by consuming contaminated water or food or by having contact with infected people or animals.
Abdominal cramping and watery diarrhea may begin suddenly, sometimes accompanied by nausea, vomiting, fever, and weakness.
Doctors diagnose the infection by examining or analyzing a stool sample for signs of the parasite.
Adequate sanitation and hand washing can help prevent spread of the infection, as can boiling water before drinking it.
Healthy people often recover on their own, but they may require treatment with an antiparasitic drug.
People with AIDS or a weakened immune system may continue to have diarrhea even when they are treated with an antiparasitic drug.

(See also Overview of Parasitic Infections.)
Cryptosporidium parasites are protozoa that infect people and many kinds of animals throughout the world.
Cryptosporidiosis is acquired by

Ingesting Cryptosporidium parasites in water or food contaminated by human or animal feces containing the parasite