The cryptosporidium parasite is a single-celled organism that infects humans. Symptoms of cryptosporidium infection include:

• Fever.
• Severe diarrhea.
• Abdominal pain.
• Weight loss.

Cryptosporidium infects an estimated 300,000 people in the United States each year. The incidence is highest in day care centers and institutional settings. Cryptosporidium is often spread by contaminated hands, although this can usually be prevented with thorough hand-washing.

The use of manure to fertilize salad vegetables is a possible source of infection.