Last Reviewed: March 2023

What is cryptosporidiosis?

Cryptosporidiosis, commonly known as Crypto, is caused by a tiny parasite called Cryptosporidium and gives an infected person diarrhea (loose stool/poop). The parasite lives in the gut of infected animals and people and spreads to others through drinking contaminated water, swimming or going into contaminated recreational water sources (i.e. pools, waterparks, lakes), eating contaminated food, or contact with infected animals. Cryptosporidium is a leading cause of waterborne disease in the United States. Cryptosporidium can survive for long periods in chlorinated drinking and swimming pool water.

Who gets cryptosporidosis?

Anyone can get cryptosporidiosis. People with severely weakened immune systems (for example, those who have cancer, HIV/AIDS, or a transplant), young children, and pregnant women may develop more serious illness than healthy persons. People who are more likely to become infected include:

  • Children who attend childcare centers, including children who wear diapers
  • Childcare workers
  • Parents of infected children
  • People who take care of other people with cryptosporidiosis
  • International travelers
  • Backpackers, hikers, and campers who drink unfiltered, untreated water
  • People who drink from untreated shallow, unprotected wells
  • People, including swimmers, who swallow water from contaminated sources
  • People who handle infected young and adult cows, sheep, deer, and goats
  • People exposed to human feces (poop) through sexual contact

How is cryptosporidiosis spread?

Cryptosporidiosis is spread though the feces (poop) of infected humans and animals. An infected person can shed Cryptosporidium once symptoms begin and for weeks after symptoms stop. Cryptosporidiosis is most often spread by:

  • Swallowing recreational water (water in swimming pools, waterparks, fountains, lakes, rivers) contaminated with cryptosporidiosis
  • Drinking untreated water from a lake or river that is contaminated
  • Swallowing contaminated water, ice, or beverages
  • Eating undercooked food or drinking raw (unpasteurized) apple cider or milk
  • Touching your mouth with contaminated hands. Hands can become contaminated in a variety of ways. For example, touching surfaces or objects (i.e. toys, bathroom fixtures, changing tables, diaper pails) that are contaminated, changing diapers, and caring for an infected person
  • Contact with an infected animal
  • Exposure to feces from an infected person through oral-anal contact

What are the symptoms of cryptosporidiosis and when do they appear?

The most common symptom is watery diarrhea (loose stool/poop). Abdominal cramping, dehydration (loss of water in the body causing weakness or dizziness), nausea (a feeling of sickness in the stomach), vomiting, fever, headache, and loss of appetite may also occur. Some people infected with cryptosporidiosis may not get sick at all.

People become ill 2 to 10 days (average 7 days) after exposure to Cryptosporidium. Symptoms usually last about 1 to 2 weeks in healthy persons, but can last longer.

How is cryptosporidiosis diagnosed?

The infection is diagnosed by identifying the parasite during a microscopic examination of the stool (poop) in a laboratory test. When a person who has diarrhea is suspected of having cryptosporidiosis, the healthcare provider should specifically ask for a Cryptosporidium test. Providers seeing people with weakened immune systems (for example, those with cancer, HIV/AIDS, or a transplant) with diarrhea should specifically request cryptosporidiosis testing.

How is cryptosporidiosis treated?

Most people with a healthy immune system will recover without treatment. People with cryptosporidiosis should drink plenty of fluids to remain hydrated and avoid dehydration (loss of water in the body causing weakness or dizziness). Some people may be prescribed an antiparasitic drug by their health care provider. An antiparasitic drug called nitazoxanide is available for people with healthy immune systems.

What can be done to prevent the spread of cryptosporidiosis?

People can decrease the chances of getting and spreading cryptosporidiosis by following these precautions:

  • Wash hands with soap and clean water for at least 20 seconds and dry them with a paper towel or air (alcohol based sanitizers do not effectively kill Cryptosporidium)
    • Before preparing or eating food
    • After using the toilet
    • After changing diapers or cleaning up a child who has used the toilet
    • Before and after caring for someone who is ill with diarrhea (loose stool/poop)
    • After handling an animal, particularly young livestock, or its feces (poop)
    • After gardening, even if wearing gloves
  • Exclude children who are ill with diarrhea from child care settings
  • Do not swim for at least two weeks after diarrhea stops
  • Do not swallow water when swimming in recreational water sources (pool, waterpark, fountain, lake, river, etc.)
  • Do not drink untreated water from lakes, rivers, springs, ponds, streams or shallow wells
  • If you are not sure about the safety of drinking water, use commercially bottled water; or use water that has been previously boiled for 1 minute and left to cool (elevations above 6,500 feet boil for 3 minutes); or use a filter (NSF '53', NSF '58', or 'absolute pore size of 1 micron or smaller')
  • Do not use (i.e. brushing teeth) or drink inadequately treated water or use ice when traveling in countries where the water might be unsafe
  • Clean household properly after a person is infected with Cryptosporidium
    • Wash linens, clothing, dishwasher- or dryer-safe soft toys, etc. as soon as possible using laundry detergent and hot water; machine dry at highest heat setting
    • For surfaces: remove all visible feces, clean with soap and water, let dry completely for at least 4 hours; if possible expose to direct sunlight during the 4 hours