Cryptosporidiosis is an infection in the intestines. It is a minor problem for most people. But, it can be life-threatening for young children, the elderly, and people who have weakened immune systems.

The Intestines

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A certain parasite causes cryptosporidiosis. It often enters the body by when you swallow food or drink that has the parasite. It can also be passed from contaminated water, soil, or stool. Common ways include:

  • Water from lakes, streams, hot tubs, swimming pools, or water parks
  • Ice cubes
  • A baby's dirty diapers
  • Touching animals, cleaning cages, or going to barns or petting zoos
  • Eating food grown in soil
  • Eating or drinking unpasteurized dairy products or apple cider
  • Oral to anal contact during sex

Once in the intestine, the parasite comes out of its shell. It then multiplies which causes symptoms.

Risk Factors

Risk is higher for:

  • Young children, especially those in day care
  • Day care workers or those who work in a group setting
  • Backpackers, hikers, and campers who recreate in contaminated water sources
  • People whose immune system is weakened by cancer, HIV, or an organ transplant
  • People who have oral to anal contact during sex


Most people don’t have symptoms. If they do appear, they may cause:


The doctor will ask about your symptoms and past health. You may have a physical exam and stool tests.


Most people will not need care. The infection will go away on its own.

Care may be needed for those with severe and longer lasting infection. Care may involve:

  • IV fluids
  • Medicine to control diarrhea
  • Antiparasitic medicine


To lower your chances of cryptosporidiosis:

Wash your hands often, mainly:

  • After using the toilet.
  • After changing a diaper.
  • Before handling or eating food.
  • After being with animals or in soil.
  • After being with people who are sick.

In general:

  • Use water you know is safe. If you have any doubts, don’t use it.
  • Try not to swallow while recreating in water.
  • Wash fruits and vegetables in safe water.
  • Don’t eat or drink unpasteurized dairy products or apple cider.
  • Use barriers when you have oral sex.

Centers for Disease Control and Prevention

IDSA—Infectious Diseases Society of America


Canadian Public Health Association

Health Canada


Cryptosporidiosis. New York Department of Health website. Available at: Accessed May 29, 2021.

Parasites—cryptosporidium (also known as crypto). Centers for Disease Control and Prevention website. Available at: Accessed May 29, 2021.

Foodborne illnesses. EBSCO DynaMed website. Available at: Accessed May 29, 2021.

Last reviewed May 2021 by David L. Horn, MD, FACP  Last Updated: 6/3/2021