Cryptosporidium enteritis is an infection of the small intestine that is caused by the parasite cryptosporidium. The main symptom is diarrhea.

Cryptosporidium has recently been recognized as a worldwide cause of diarrhea in all age groups. Its major impact has been among those with weakened immune systems, including:

• People who take medications to suppress their immune system
• People with HIV or AIDS
• Transplant recipients

In these groups, this diarrheal infection is not just bothersome. It also can lead to severe, and potentially life-threatening, loss of muscle and body mass (wasting) and malnutrition.

The major risk factor is swallowing water contaminated with fecal matter. Those at higher risk include:

• Animal handlers
• Men who have sex with men
• People in close contact with infected individuals
• Young children

Outbreaks have been linked to:

• Drinking from contaminated public water supplies
• Drinking unpasteurized cider
• Swimming in contaminated pools and lakes