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What is giardiasis?

Giardiasis (jee-ahr-dahy-uh-sis) is a diarrheal illness caused by a parasite called Giardia. The Giardia parasite lives in the intestines of infected people and animals and forms an outer shell called a "cyst". Giardia cysts can live outside the body for long periods of time.

How common is giardiasis?

Giardia is found throughout the United States and the world, and is especially common in countries without clean drinking water. In the United States, Giardia is one of the most common causes of waterborne diseases in people. Outbreaks have been associated with contaminated municipal and recreational waters, day care centers, and among people who were exposed to feces during sex. In California, 1,700 to 2,000 cases of giardiasis were reported each year during 2008-2010. However, it is likely that there are many more cases each year that go undiagnosed.

How do people get giardiasis?

Giardiasis is a contagious disease. When a person or animal infected with Giardia begins to have symptoms, millions of cysts are shed in their feces during a bowel movement. The shedding of the cysts can last for weeks after the symptoms stop.

People can become infected after accidentally swallowing Giardia cysts. Giardia may be found in soil, food, water, or on surfaces that have been contaminated with feces from infected people or animals. Chlorine in swimming pools will not necessarily kill Giardia. It can also be spread from one person to another in day care centers caring for children in diapers and during unprotected oral-anal sex.

What are the symptoms of giardiasis?

Symptoms can begin one to two weeks after becoming infected with the Giardia cysts. Symptoms include:
  • Diarrhea
  • Abdominal cramps
  • Nausea
  • Bloating
  • Gas
  • Fatigue
  • Weight loss
  • Dehydration
In otherwise healthy persons, symptoms usually last two to six weeks, but sometimes last longer. Some infected people do not develop any symptoms.

How is giardiasis diagnosed?

Giardiasis can be diagnosed by your health care provider by looking for the cysts in a sample of feces under a microscope or using special tests. Because the cysts are not in the feces all the time you may be asked to repeat the test several times.

How is giardiasis treated?

There are several prescription drugs available to treat Giardia.

What can a person do to prevent giardiasis?

  • Wash hands with soap and water for at least 20 seconds, rubbing hands together vigorously and scrubbing all surfaces:
    • Before preparing or eating food
    • After using the toilet
    • After changing diapers or cleaning up a child who has used the toilet
    • Before and after tending to someone who is ill with diarrhea
    • After handling an animal or animal waste
  • Avoid swallowing recreational water (water parks, swimming pools, hot tubs, lakes, streams).
  • Purify drinking water from questionable sources by boiling, filtration, or iodine treatments. For more information on treating and filtering water when travelling in backcountry areas visit the U.S. Centers for Disease Control and Prevention (CDC) websites on backcountry water treatment  and a guide to water filters.
  • Use condoms or barriers to avoid fecal exposure during anal or oral-anal sex.
  • Practice extra precaution when travelling outside the U.S., especially in countries where the drinking water may not be clean visit the  CDC Food and Water Safety webpage.

How do I protect others if I have diarrhea or giardiasis?

  • Use careful and frequent hand washing to prevent spread to others in your household.
  • Avoid preparing food for others until the diarrhea has stopped for 48 hours or you are under treatment. If you must prepare food for others in your household, be sure to wash your hands frequently.
  • Avoid sexual activities that may allow others to come into contact with your feces or anal area.

Food handlers with diarrhea or giardiasis 

If you have diarrhea you should stop working until 48 hours after diarrhea has stopped.

Children with diarrhea or giardiasis

Children with diarrhea should be kept out of child care settings until 48 hours after diarrhea has stopped.

At recreational water venues (pools, water slides, interactive fountains, lakes, ocean)

  • Do not swim or participate in recreational water activities if you have diarrhea (this is essential for children in diapers). 
  • Shower before entering the water.
  • Wash children thoroughly (especially their bottoms) with soap and water after they use the toilet or their diapers are changed and before they enter the water. 
  • Take children on frequent bathroom breaks and check their diapers often.
  • Change diapers in the bathroom, not at the poolside.

What is public health doing about giardiasis?

The California Department of Public Health (CDPH) and local health departments (LHDs) monitor giardiasis in California. If many cases are reported, CDPH and LHDs will investigate to find the cause, fix the problem, and educate the public.

To help prevent spread of giardia to others, LHDs may restrict persons with giardia from certain types of work (such as food handling) or other activities until the person has not had diarrhea for 48 hours.

Where can I get more information about giardiasis?

You can get more information on giardiasis from your health care provider, your local health department, and from the U.S. Centers for Disease Control and Prevention giardia website.

March 2015 ​ ​​
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