Cryptosporidium FAQ

• What is Cryptosporidium and how is it transmitted?

• What are the symptoms?

• Who is at risk for severe cryptosporidiosis?

• Why is Cryptosporidium a problem in drinking water?

• How can I tell if there is Cryptosporidium in my drinking water?

• Is there a cure for Cryptosporidium infection?

• Should I take extra protective measures?

• What can immunosuppressed persons do to avoid infection with Cryptosporidium?

Q. What is Cryptosporidium and how is it transmitted?

A. Cryptosporidium is a microscopic parasite that is found in the feces of infected humans or animals. Humans are infected when they ingest contaminated water or food, or touch contaminated objects, then touch their mouth before washing their hands well. Cryptosporidiosis, the disease caused by Cryptosporidium, is one of the most common causes of diarrhea among persons with AIDS in the U.S.

Q. What are the symptoms?

A. Symptoms of Cryptosporidium infection in persons with normal immune systems include diarrhea that lasts 1 to 2 weeks, often accompanied by abdominal cramps, fatigue, nausea, vomiting, and low-grade fever. People usually develop symptoms 2 to 10 days after ingesting the parasite. In persons with weakened immune systems, cryptosporidiosis can be chronic and life-threatening.

Q. Who is at risk for severe cryptosporidiosis?

A. People at risk for severe cryptosporidiosis include people with AIDS, people who have cancer, or organ or bone marrow transplant patients who are taking drugs that suppress the immune system, and people who are born with genetically weakened immune systems.

Q. Why is Cryptosporidium a problem in drinking water?

A. Cryptosporidium is a problem because most water from lakes, rivers, and streams, contains some of the microscopic parasite. Most communities get their drinking water from these "surface" sources, rather than from underground sources such as wells. Cryptosporidium is highly resistant to chlorine and other disinfectants, which are used to kill bacteria and viruses in drinking water. In addition, Cryptosporidium is so small that it is not easily removed from water by the type of filters used in conventional municipal water treatment. Over half of the tested public water supplies that use surface water have been found to have small amounts of Cryptosporidium in the water sent to homes and businesses.

Q. How can I tell if there is Cryptosporidium in my drinking water?

A. You cannot tell without expensive, special tests. These tests are not very good for home use, and are not always reliable.

Q. Is there a cure for Cryptosporidium infection?

A. No. Some drugs, such as paromomycin (PAR-o-mo-my-sin), may reduce the symptoms of cryptosporidiosis, but no drug now known can cure it. Diarrhea can cause dehydration. Persons with diarrhea should contact their health care provider who may recommend an oral rehydration therapy mix.

Q. Should I take extra protective measures?

A. It depends on your health and your drinking water. If you have AIDS, if you have cancer or if you have had an organ or bone marrow transplant or are taking drugs that weaken your immune system, or if you were born with a genetically weakened immune system, you may want to take extra measures. You should talk to your health care provider regarding the level of your risk and on how to reduce it. If you have a healthy immune system, you are at less risk for cryptosporidiosis, but you may want to consider the quality of your drinking water. For more information, refer to the publication Cryptosporidium: What you need to know to protect yourself. 

Q. What can immunosuppressed persons do to avoid infection with Cryptosporidium?

A.  Follow these recommendations:

• Avoid sexual practices that may result in exposure to feces.

• Avoid drinking water directly from lakes, rivers, ponds, or streams.

• Avoid swimming in lakes, rivers, streams, ponds, public swimming pools, or recreational water parks.

• Avoid working with diaper-aged children.

• Avoid contact with feces of all animals, particularly young farm animals such as calves.

• Always wash hands thoroughly: after any contact with animals, after any contact with soil (e.g., gardening), after changing diapers, before eating, or before preparing food.

• Consume only water that has been purified by boiling for 1 minute, or by treatment with certain filters. 

For more information, refer to the publication Cryptosporidium: What you need to know to protect yourself.

This FAQ was written by David G. Addiss, Susan Goldstein, Dennis D. Juranek, and Thomas Navin of the Centers for Disease Control and Prevention, Atlanta, USA.