Cryptosporidium infection (Cryptosporidiosis)

Cryptosporidiosis is a diarrheal illness caused by the parasite Cryptosporidium. Anyone can get this infection. However, it causes more severe illness in people with impaired immune systems, such as people living with HIV.

You can become sick by drinking water or eating food that is contaminated with the parasite. You can also become infected by touching stool or objects contaminated by stool, and then touching your mouth with unwashed hands. Some people become sick after swimming in public pools contaminated with stool from infected people. Sexual practices that result in hand or mouth contact with stool can also spread the infection.


Symptoms include:

  • Watery diarrhea
  • Abdominal cramping
  • Vomiting
  • Low-grade fever
  • Loss of appetite
  • Weight loss
  • Dehydration

Symptoms usually begin one to 12 days after exposure, and may last for one to two weeks. But infection may last longer for people with weak immune systems. Some people may not have any symptoms at all.


  • Practice good hand hygiene: Wash your hands with soap and warm water before touching food, and after using the toilet, changing diapers, handling animal stool or gardening.
  • Avoid water that may be contaminated: Do not drink water directly from streams, lakes, springs or swimming pools. If you must drink from these sources, boil the water for at least one minute or use a filter with a pore size of one micron or smaller.
  • Avoid food that may be contaminated: Wash all fruits and vegetables, and do not drink unpasteurized milk, milk products and apple cider.
  • Take extra care when traveling: When traveling to countries with poor water or food sanitation, avoid raw fruits and vegetables, unboiled tap water, ice and food from street vendors.
  • Protect yourself and others: If you are infected, do not swim in pools or recreational water for two weeks after the diarrhea stops. Sexual practices that result in hand or mouth contact with stool (anal sex, fingering, rimming) can spread disease. To prevent illness, wash the butt, penis and any sex toys thoroughly with soap and water before and after these activities. A dental dam can also provide protection when rimming.

Diagnosis and Treatment

Health care providers can detect the infection with stool tests.

People with diarrhea, especially children and pregnant women, should drink plenty of fluids to stay hydrated. People with healthy immune systems usually get well without treatment.

Returning to Work or School

Since this parasite is found in the stool, people should stay home from work, school or day care if they cannot control their bowel movements. That includes infants, young children and people with certain types of disabilities.

Food handlers, health care workers and children in day care must get approval from the Health Department before they can return to their regular activities. That involves follow-up stool testing.

Monitoring for Cryptosporidiosis in NYC Water

Very low levels of Cryptosporidium are sometimes found in New York City's water. However, New York City treats its water with ultraviolet (UV) light to destroy this parasite. At this time there is not a significant risk of cryptosporidiosis from New York City drinking water. People with impaired immune systems can take extra precautions to avoid this infection.

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