Giardia

Note: PDFs related to this topic are also available: Facts About Giardia and Swimming Pools - PDF [PDF - 147 kb] and Datos sobre la Giardia y las piscinas [PDF - 159 kb] (translation courtesy of the New Mexico Department of Public Health).

Giardia is one of the most frequent causes of waterborne disease (drinking water and recreational water) among humans in the United States. Below are answers to the most common questions regarding Giardia and healthy swimming.

What is Giardia?

Giardia (gee-ARE-dee-uh) is a germ that causes diarrhea. This germ is found in the fecal matter of a person who has been infected by Giardia. It has a tough outer shell that allows it to survive for up to 45 minutes even in properly chlorinated pools.

The disease caused by infection with the germ Giardia is called giardiasis. Giardia is microscopic, so it can’t be seen with the naked eye.

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Why Should I Be Concerned about Giardia?

Giardia is a common cause of recreational water illness (disease caused by germs spread through pool water) in the United States and can cause prolonged diarrhea (for 1–2 weeks).

During the past two decades, Giardia has become recognized as one of the most common causes of waterborne illness in the United States. The germ is found in every part of the United States and the world.

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How is Giardia Spread at Aquatic Facilities?

Giardia is not spread by contact with blood. Giardia can be spread by:

• Swallowing recreational water contaminated with Giardia. You share the water—and the germs in it—with every person who enters the pool. This means that just one person with diarrhea can easily contaminate the water. Swallowing even a small amount of pool water that has been contaminated with the Giardia germ can make you sick. Recreational water is water from swimming pools, hot tubs, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals.
• Putting something in your mouth or swallowing something (such as food) that has come in contact with the stool of a person or animal infected with Giardia.
• Swallowing Giardia picked up from surfaces (such as lounge chairs, picnic tables, bathroom fixtures, changing tables) contaminated with stool from an infected person.

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How Do I Protect Myself and My Family?

Take action! Because Giardia can stay alive for almost an hour even in well-maintained pools, stopping the germ from getting there in the first place is essential. Making sure that your pool has the right disinfectant and pH levels to kill Giardia is also critical.

Three Steps for All Swimmers

Keep germs from causing recreational water illnesses (RWIs):

• Don't swim when you have diarrhea. You can spread germs in the water and make other people sick.
• Don't swallow the pool water. Avoid getting water in your mouth.
• Practice good hygiene. Shower with soap before swimming and wash your hands after using the toilet or changing diapers. Germs on your body end up in the water.

Three Steps for Parents of Young Kids

Keep germs out of the pool:

• Take your kids on bathroom breaks or check diapers often. Waiting to hear "I have to go" may mean that it's too late.
• Change diapers in a bathroom or a diaper-changing area and not at poolside. Germs can spread in and around the pool.
• Wash your child thoroughly (especially the rear end) with soap and water before swimming. Invisible amounts of fecal matter can end up in the pool.

Three Steps for Testing Pool Water

• Purchase pool test strips at your local home improvement or pool supply store (be sure to check the expiration date).
• Use the test strips to check pool or hot tub water for adequate chlorine (1-3 parts per million [ppm]) or bromine (2–5 ppm) and pH (7.2–7.8) levels.
• If you find improper chlorine, bromine, and/or pH levels, tell the pool/hot tub operator or owner immediately.

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For more information about Giardia, please see CDC's Giardiasis page.

If you are a pool or hot tub operator and would like more information on how to prevent Giardia and other germs from contaminating the water, please see the Education and Information for Aquatics Staff page.