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Giardia is one of the leading causes of waterborne disease, or disease caused by contaminated drinking water and recreational water. 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. 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.

Why Should I Be Concerned about Giardia?

Giardia is a leading cause of recreational water illness (disease caused by germs spread through water in the places we swim) 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 leading 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.
  • Putting something in your mouth or swallowing something (such as food) that has come in contact with the feces 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 feces 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. We all share the water we swim in, so each of us plays an essential role in helping to protect ourselves, our families, and our friends from Giardia and other germs. Remember, chlorine and other disinfectants don’t kill germs instantly. Additionally, the mixing of chlorine with pee and sweat uses up the chlorine in the pool, which would otherwise kill germs.

All swimmers should take the following easy and effective healthy swimming steps:

Keep the pee, poop, sweat, and dirt out of the water!
  • Stay out of the water if you have diarrhea.
  • Shower before you get in the water.
  • Don’t pee or poop in the water.
  • Don’t swallow the water.

Every hour—everyone out!
  • Take kids on bathroom breaks.
  • Check diapers, and change them in a bathroom or diaper-changing area–not poolside–to keep germs away from the pool.
  • Reapply sunscreen.
  • Drink plenty of fluids.

Check the free chlorine level and pH before getting into the water.
  • Pools: Proper free chlorine level (1–3 mg/L or parts per million [ppm]) and pH (7.2–7.8) maximize germ-killing power.
  • Hot tubs/spas: Proper disinfectant level (chlorine [2–4 parts per million or ppm] or bromine [4–6 ppm] and pH [7.2–7.8]) maximize germ-killing power.
  • Most superstores, hardware stores, and pool-supply stores sell pool test strips.

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

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 Information for Aquatics Staff page.

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