Giardiasis Fact Sheet

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Giardiasis is an intestinal disease caused by a parasite


Giardia lamblia is the parasite that causes giardiasis.

Anyone can get giardiasis. Those persons at increased risk are:

  • Children who attend child care centers and adults in contact with these children
  • People in close contact with children or adults who have giardiasis
  • People who travel to some foreign countries where the water supply and food may be contaminated with Giardia
  • People who drink surface water that has not been properly treated
  • Men who have sex with other men

Giardia are passed in feces (stool)

  • Giardia are passed in the feces of infected humans, wild animals, and pets.  Giardia can be passed in the feces for weeks to months, even if the person has no symptoms.
  • The parasite is spread from person to person by close contact with someone who has the organism (for example, contact with diapered children).  Outbreaks often occur in child care centers.  Feces of humans or animals also can contaminate lakes, reservoirs, and streams, and giardiasis can result when people drink the untreated water.

Symptoms to look for may include:

  • Diarrhea
  • Abdominal cramps
  • Bloating and gas

Symptoms usually begin 7 to 10 days (with a range of 3 to 25 days) after exposure to Giardia.  Many people with giardiasis do not have any symptoms.


Treatment with specific medications may shorten the illness

Giardiasis can be prevented

  • Wash hands after using the bathroom, after handling diapers, before fixing food or drink, and before eating.
  • Avoid drinking improperly treated water, for example, when camping or during foreign travel.  Municipal water supplies with filtration are usually safe.
  • Keep children with diarrhea out of swimming pools.  Have diapered children wear tight diaper covers in swimming or wading pools.
  • Maintain swimming pools through adequate disinfection and filtration.  If a child or adult has a bowel movement in a swimming pool, have everyone get out of the water, remove the stool, and increase the chlorine to 3 to 5 parts per million (ppm) for 30 minutes.  Water in unfiltered wading pools should be emptied and refilled.
  • In child care centers, careful handwashing among staff and children is very important.