Frequently Asked Questions

Giardia is found in the feces of infected animals or humans. To become infected, a person must consume contaminated food or water including drinking from streams or rivers.

In Washington State, 700 to 900 cases of giardiasis are reported annually. The most common exposures reported by Washington residents include recreational water exposure and international travel.

Anyone can get giardiasis. Persons more likely to become infected include:

• People who drink water or use ice made from contaminated sources (e.g., lakes, streams, shallow or
• poorly monitored or maintained wells). Contaminated water may include water that has not been boiled, filtered, or disinfected with chemicals.
• People who swallow contaminated water while swimming, especially in lakes, rivers, springs, ponds,
• and streams. Several community-wide outbreaks have been linked to recreational water or drinking water contaminated with Giardia.
• People who eat uncooked food that contains Giardia organisms.
• Children in childcare settings.
• Close contacts (such as those in the same family or in the same household or childcare setting) or caregivers of infected people.
• International travelers.
• People exposed to human feces through sexual contact.

Giardia infection can cause a variety of intestinal signs or symptoms, which include:

• Diarrhea
• Gas or flatulence
• Greasy or foul smelling stools
• Stomach or abdominal cramps
• Upset stomach or nausea

These symptoms may lead to weight loss and dehydration. Some people with Giardia infection have no symptoms at all.  Symptoms may last 2 to 6 weeks, but can sometimes last longer. Medications can help decrease the amount of time symptoms last.

Anything that comes in contact with feces from infected humans or animals can become contaminated with the Giardia parasite. People become infected when they swallow the parasite. Giardiasis is commonly spread person to person when the ill person does not adequately wash their hands after using the toilet and then contaminates another person’s food or drink. Lastly, Giardia is sometimes found in water or on surfaces, or soil contaminated with the feces from infected humans or animals.

Symptoms of giardiasis can begin between 3 to 25 days after becoming infected, with the average being between 7 to 10 days.

Giardia infection can cause lingering symptoms and complications, especially in infants and children under 5. The most common complications include:

• Dehydration. Often a result of severe diarrhea, dehydration occurs when the body doesn’t have
• enough water to carry out its normal functions.
• Failure to thrive. Chronic diarrhea from Giardia infection can lead to malnutrition and harm a child’s
• physical and mental development.
• Lactose intolerance. Many people with Giardia infection develop lactose intolerance — the inability to properly digest milk sugar. The problem may persist long after the infection has cleared, leading to weight loss in some people.