Cryptosporidiosis - Fact Sheet


What is cryptosporidiosis?
Cryptosporidiosis is an intestinal illness caused by a one-cell parasite called Cryptosporidium parvum.

Where are Cryptosporidium parasites found?
Cryptosporidium parasites live in the intestines of infected people, cattle, and other domestic animals (e.g., cats and dogs).

How does this parasite spread?
The Cryptosporidium parasite is passed in the stool of an infected person or animal as an oocyst (egg). Ingestion of only a few oocysts in contaminated food or water can make a person ill. Person-to-person and animal-to-person transmission can occur.

Who gets cryptosporidiosis?
People who are most likely to become infected with Cryptosporidium include the following: children who attend day care centers, including diaper-aged children; child care workers; parents of infected children; international travelers; backpackers, hikers, and campers who drink unfiltered, untreated water; swimmers who swallow water while swimming in swimming pools, lakes, rivers, ponds, and streams; people who drink from shallow, unprotected well; and people who swallow water from contaminated sources.

What are the symptoms of cryptosporidiosis?
Frequent, nonbloody, watery diarrhea is the most common symptom of cryptosporidiosis. The diarrhea is associated with cramping abdominal pain. Fever, loss of appetite, nausea, and vomiting occur less often. Some infected persons may not have any symptoms.

How soon do symptoms appear?
The symptoms may begin 2 - 10 days after exposure (average 7 days).

How long can an infected person carry Cryptosporidium?
Oocysts, the infectious stage, will appear in the stool at the onset of symptoms and can continue to be passed in the stool for several weeks after symptoms end.

What is the treatment for cryptosporidiosis?
There is no specific treatment. When indicated, rehydration has proven to be effective. It is a self-limiting illness in people with healthy immune systems.

What can be done to prevent the spread of cryptosporidiosis?
Some important preventive measures are:

  • Thoroughly wash hands after toilet visits and before eating or handling food.
  • Wash all fruits and vegetables thoroughly, especially those that will not be cooked.
  • Avoid consuming improperly filtered water from rivers, lakes, water parks, or swimming pools.
  • Wash hands after contact with calves and other animals with diarrhea.
  • Immunocompromised persons may consider boiling drinking water for 1 minute or using a water filter. Only filters capable of removing particles 0.1-1.0 µm in diameter should be considered. Chemical disinfectants are not effective against oocysts.
  • Persons at increased risk should avoid sexual practices that involve possible contact with stool.


This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.


For additional information on this disease, visit the Centers for Disease Control and Prevention website.







To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.