What is cryptosporidiosis?

Cryptosporidiosis, sometimes referred to as "Crypto," is a diarrheal infection caused by the parasite Cryptosporidium. The parasite is most commonly acquired after drinking or swallowing food or water contaminated with feces, including water swallowed while swimming. Infection can also occur after contact with objects or surfaces contaminated with feces, and from person-to-person contact with an infected individual. Because the parasite is protected by an outer shell that allows it to survive for long periods of time outside the body, it is very resistant to chlorine disinfection. In the United States, Cryptosporidium is one of the most common causes of waterborne disease.  

Where does cryptosporidiosis occur?

Cryptosporidium is prevalent throughout the world. Travelers to developing countries who visit rural areas, hike or trek in backcountry areas, or frequently eat or drink in areas where sanitation is poor are at greatest risk of contracting the disease. Outbreaks of cryptosporidiosis have also occurred in the United States when water supplies or swimming pools become contaminated.

How is cryptosporidiosis spread?

The disease is spread by accidentally swallowing anything that has come into contact with the feces of a person or animal with the infection. This includes:

  • Swallowing water contaminated with cryptosporidiosis. The infectious stage of the parasite, called an oocyst, can be transmitted by swallowing water from swimming pools, hot tubs, jacuzzis, lakes, rivers, springs, ponds, or streams contaminated with sewage or feces (from either humans or animals).

  • Eating uncooked foods contaminated with the parasite.

  • Swallowing the parasite picked up from surfaces contaminated with the stool of an infected person. This includes bathroom fixtures, changing tables, and diaper pails.

Who is at risk for cryptosporidiosis?

While cryptosporidiosis is normally not a serious disease in healthy individuals, for people with a severely weakened immune system, it can lead to a serious or life-threatening illness. This includes people with:


  • Cancer and transplant patients who are taking certain immunosuppressive drugs

  • Inherited diseases that affect the immune system

What are the symptoms of cryptosporidiosis?

The following are the most common symptoms of cryptosporidiosis. However, each individual may experience symptoms differently. Symptoms may include:

  • Diarrhea

  • Loose or watery stools

  • Vomiting

  • Weight loss

  • Stomach cramps

  • Fever

Some infected people may not develop any symptoms. If symptoms do develop, they often last approximately two weeks and sometimes longer. However, whether or not you have symptoms, the parasite is passed in the stool for up to two months, posing a risk of spreading the infection to others.

How can cryptosporidiosis be prevented?

The best ways to prevent cryptosporidiosis are through good personal hygiene, avoiding unsafe water sources, and avoiding unboiled water and uncooked foods in areas known to have poor sanitation.

  • Wash hands thoroughly with soap and water after using the toilet or changing diapers.

  • Wash hands thoroughly before eating or preparing food.

  • Wash and peel all raw fruits and vegetables before eating.

  • Avoid drinking water from lakes, rivers, springs, ponds, or streams, unless they have been filtered and chemically treated.

  • Avoid any water or food that may be contaminated.

  • When traveling to countries where the water supply may be unsafe, avoid drinking unboiled tap water and avoid eating any raw foods washed with tap water. Choose steaming hot drinks, such as coffee and tea, and pasteurized fruit drinks. If choosing bottled water, make sure it is bottled water that is safe to drink.

  • Many home water filters are designed to remove Cryptosporidium. Read the label for details. 

No vaccine or medication is available to prevent cryptosporidiosis. 

How is cryptosporidiosis diagnosed?

Diagnosis of cryptosporidiosis is made through examination of stool samples to determine if they are infected. Because tests for this disease are not routinely done in laboratories, special testing for the parasite must be done.

Treatment for cryptosporidiosis

There is no completely effective treatment for cryptosporidiosis, and people with a healthy immune system generally recover on their own. People who are in poor health or have a weakened immune system risk a more serious infection. In some cases, doctors may prescribe the drug nitazoxanide to treat diarrhea symptoms in those who are otherwise healthy. In general, it's important to drink plenty of fluids to replace those lost through diarrhea. Specific treatment for cryptosporidiosis will be determined by your doctor based on:

  • Your overall health and medical history

  • Extent of the disease

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the disease

  • Your opinion or preference