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Giardia Infections
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Giardia Infections

Giardiasis is an intestinal illness caused by the parasite Giardia intestinalis, typically contracted through contaminated water, food, or surfaces.

Overview

Giardiasis is an illness caused by a parasite called Giardia intestinalis. It lives in soil, food, and water, and may be found on surfaces contaminated with waste. You can become infected by swallowing the parasite or through exposure to human feces via sexual contact.

Risk Factors

The risk of getting giardia is higher for:

  • Travelers to countries where it is common.
  • People in child care settings.
  • Those who drink untreated water.

Symptoms

Diarrhea is the main symptom of a giardia infection. Other symptoms include:

  • Passing gas
  • Greasy stools
  • Stomach cramps
  • Upset stomach or nausea

These symptoms may lead to weight loss and loss of body fluids. Some people have no symptoms at all. Symptoms often last two to six weeks.

Diagnosis & Treatment

Stool sample tests are used to diagnose the infection, often requiring the collection of several samples. Doctors use several drugs to treat the condition.

Prevention

The best way to prevent infection is to practice good hygiene, including frequent hand washing. Do not drink water that may be contaminated, and always peel or wash fresh fruit and vegetables before eating.

Source: Centers for Disease Control and Prevention

Frequently Asked Questions

Yes, Giardia can be transmitted through sexual contact, particularly through oral-anal contact. This is because the parasite can be present in fecal matter, and swallowing the organism, even in microscopic amounts, is sufficient to cause infection. Safe sex practices and thorough hygiene are essential for prevention in this context.
single negative stool test does not rule out the infection, as the parasite is not always present in every stool sample. Doctors often require multiple stool samples collected over several days or weeks to increase the likelihood of detection. In some cases, a blood test for antibodies or an endoscopy with a duodenal aspirate may be used if stool tests remain inconclusive.
Drinking directly from untreated natural water sources is risky because Giardia cysts can survive in cold water and are not removed by standard household filters. To prevent infection, you should boil water for at least one minute, use a filter specifically rated to remove protozoa (with a pore size of 1 micron or less), or use chemical purification tablets designed to kill Giardia.
Symptoms usually appear within one to two weeks after exposure, though the incubation period can range from one to twenty-five days. It is important to note that some individuals may carry the parasite without developing any symptoms at all, which can make transmission to others more difficult to track.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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