Updated: May 21, 2026
What is Cryptosporidiosis?
Cryptosporidiosis (krip-toe-spo-rid-e-o-sis), is a diarrheal disease caused by a microscopic parasite from the genus Cryptosporidium. Both the disease and the parasite are more commonly known as "Crypto." It can live in the intestine of humans and animals and is passed in the stool of an infected person or animal. Crypto has become recognized as one of the most common causes of waterborne disease in humans in the United States. The parasite is found in every region of the United States and throughout the world.
What are the symptoms?
Symptoms typically appear 2–10 days after infection, with an average onset of 7 days. In individuals with healthy immune systems, symptoms usually resolve within 2–3 weeks.
Common symptoms include vomiting, diarrhea, loose or watery stool, stomach cramps, upset stomach, and a slight fever. Some people have no symptoms.
Crypto infections primarily affect the small intestine; however, for those with weakened immune systems, the infection can spread to other parts of the digestive tract (such as the biliary tract or pancreas) or even the respiratory tract. Severe cryptosporidiosis can lead to chronic illness or life-threatening complications related to nutrient absorption and digestion, as well as increasing weakness and muscle wasting.
How is Cryptosporidiosis treated?
Anti-diarrheal medications may help reduce diarrhea, but it’s important to consult a health care provider before taking them.
Your health care provider may also prescribe nitazoxanide, which is an FDA-approved medication for treating cryptosporidiosis in individuals with healthy immune systems who are at least one year old. The effectiveness of nitazoxanide in treating cryptosporidiosis in individuals with weakened immune systems is uncertain.
How do people catch this disease?
People generally become infected after accidentally swallowing the parasite. Crypto may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals. Typical examples of how Crypto can be spread include the following:
- By putting something in your mouth (or accidentally swallowing something) that has come in contact with the stool of a person or animal infected with Crypto.
- By swallowing recreational water contaminated with Crypto. Recreational water is water in swimming pools, hot tubs, jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals. Crypto is chlorine resistant and can live for days in pools.
- By eating uncooked food contaminated with Crypto.
Additionally, Crypto can be shed in person's stool starting when symptoms begin and may continue for up to two weeks after symptoms have ended. This means they can still spread the infection to others, even after symptoms like diarrhea have stopped.
What can be done to stop the spread of this disease?
- Washing your hands with soap and water after using the toilet, changing diapers, and before eating or preparing food is the best way to stop the spread of Crypto.
- Avoid swallowing recreational water, water that might be contaminated, and untreated water from shallow wells, lakes, rivers, springs, ponds, and streams.
- Individuals should avoid using ice, or drinking untreated water, when traveling in countries where the water supply might be unsafe.
- Avoid swimming in recreational water (pools, hot tubs, lakes or rivers, the ocean, etc.) if you have Crypto, and for at least 2 weeks after diarrhea stops. You can pass Crypto in your stool and contaminate water for several weeks after your symptoms have ended.
- Wash and/or peel all raw vegetables and fruits before eating. Use treated water to wash all food that is to be eaten raw. Avoid eating uncooked foods when traveling in countries with minimal water treatment and sanitation systems.