What Are Giardia Infections?

Medically reviewed by Ronald Lubelchek, MD

Giardia is a parasite—or a tiny organism—that lives in soil, food, and water. The parasite can make you sick if it enters your body. If you become infected by Giardia, the parasite lives in your intestines, causing diarrhea and other digestive issues.

Giardia infections, also known as giardiasis, mostly affect children under four years old in the United States. Children can get the infection through public swimming areas (e.g., pools or lakes) and childcare settings (e.g., daycare or school). Most cases of Giardia infections are unreported, but an estimated 1 million people in the U.S. experience the infection annually.

Symptoms

Giardia affects each person differently. While some people experience severe symptoms, about half of the people with the infection don't have symptoms at all. If you do have symptoms, you might experience:

• Diarrhea

• Gas

• Foul-smelling stool (poop)

• Stomach cramps or pain

• Nausea or vomiting

• Fatigue

Less common symptoms of a giardia infection include fever, skin lesions, and joint pain. Additionally, children with the infection are more likely to have stomach pain, while adults tend to experience more diarrhea.

It is also common to experience dehydration as a result of diarrhea, particularly when diarrhea lasts several days. This dehydration may cause you to lose weight, as well as stop your body from absorbing important nutrients like fat, lactose, vitamin A, and vitamin B12.

Causes

You can get sick with a Giardia infection if you swallow Giardia through contaminated water or make contact with someone with giardiasis. For example, if you swallow drinking water or water in a pool, lake, or river that is contaminated with Giardia, you might get an infection.

Some of the other ways Giardia spreads are:

• Changing diapers without proper handwashing (especially common in daycares)

• Eating food contaminated with Giardia

• Having sexual contact with someone who currently has or recently had giardiasis

• Touching a contaminated surface (e.g., bathroom door) and then transferring the germs to your mouth

• Being near infected animals or in an environment contaminated with poop

In addition, in areas with limited access to toilets and safe, clean water, Giardia can spread more easily. For example, one study found that not having a household toilet, not washing hands before eating or after playing with animals, not boiling water before drinking, bathing in the river, and not wearing shoes outside were all risk factors for giardiasis.

Related:Health Issues That Can Be Caused by Floodwater

Diagnosis

If you think you may have giardiasis, it’s important to seek care from your healthcare provider. They will most likely ask you to collect a stool (poop) sample for them to test. In some cases, multiple samples might be necessary because it can be hard to detect Giardia through laboratory tests.

During your appointment, your provider may also ask if you:

• Recently traveled internationally

• Spent time in the woods or forest

• Have been exposed to unsanitary water

• Work in a daycare or childcare setting

• Had sex with someone who may have had giardiasis

Treatment

If your healthcare provider diagnoses you with giardiasis, they may provide you with prescription medications to help reduce your symptoms. If your symptoms are not severe, sometimes, they may wait to see if symptoms resolve on their own before giving treatment.

The most common medicine that providers prescribe for a Giardia infection is Nuvessa (metronidazole) which is a pill you take one to three times a day for five to 10 days.

Because giardiasis can cause dehydration, your treatment regimen can sometimes include rehydration through drinking fluids or receiving an IV. Pregnant people and infants are at especially high risk for dehydration.

How to Prevent Giardia Infections

Proper hygiene can help prevent Giardia from spreading—therefore, it's important to wash your hands with soap and water, especially before cooking or eating and after using the bathroom or changing a diaper.

To make sure water is safe to drink, you boil the water for one minute, use a filter that can take out harmful chemicals or toxins, or choose to drink bottled water. If you suspect the water might be contaminated, don’t use it to wash or prepare food without boiling or filtering it.

In addition, there are precautions you can take in specific settings to reduce the risk of Giardia spreading more easily:

Childcare Settings

• Keep children home from school if they have diarrhea

• Clean and disinfect toys and surfaces regularly

• Use proper diapering techniques, including disposing of diapers and clothing with poop on them and washing your hands after

While Swimming

• Do not swallow water

• Do not swim if you have diarrhea

• Shower before getting in the water

• Take young children on bathroom breaks and check diapers every hour

With Animals

• Minimize contact with poop

• Wash your hands after interacting with an animal

• Avoid touching your face until you have washed your hands

During Sex

• Avoid having oral, vaginal, or anal sex for several weeks after you or your partner had giardiasis

• Use condoms or dental dams

• Wash your hands, genitals, and anus before and after sex
  

On Different Surfaces

If you, someone who lives in your house, or your pet recently had a giardia infection, it’s important to clean and disinfect your surfaces and objects to remove Giardia germs from your home. You may consider trying the following techniques for different types of surfaces and objects:

Complications

The main complication of giardiasis is dehydration. If you have the infection, make sure to drink a lot of water and other fluids. If you are pregnant or caring for an infant, it's important to talk with your or your child’s healthcare provider about treatment options.

Other complications that may arise due to a Giardia infection include irritable bowel syndrome, chronic fatigue syndrome, food allergies, or joint pain due to reactive arthritis. If you are experiencing symptoms of any of these complications, speak with your healthcare provider about how to manage symptoms.

Living With a Giardia Infection

Generally speaking, if you become infected with Giardia, your symptoms should resolve within a few weeks. Symptoms generally begin about one to two weeks after you’re exposed and last two to six weeks, with most symptoms resolving on their own (without treatment) within four weeks.

People who have a weakened immune system—such as those living with HIV or an autoimmune condition—may be more likely to have symptoms that last longer. If you are immunocompromised, talk to your healthcare provider about options that can help reduce your symptoms.

Frequently Asked Questions

What kills Giardia over the counter?

Depending on the type of surface, you can remove Giardia germs with typical cleaning solutions and a household disinfectant.

Should I stay home if I have a Giardia infection?

You do not need to stay home if you are infected by Giardia, but you should avoid swimming, particularly while experiencing diarrhea. If your child has diarrhea because of a Giardia infection, it's a good idea to keep them home from school until they have normal poops.

How long are humans contagious with Giardia infections?

Giardia spreads when you come into contact with the poop of an infected person or animal. Because the parasite can remain in poop for weeks after initial symptoms, people can spread the infection for weeks after they are feeling better. Make sure to practice proper hand washing and other hygiene techniques to minimize germs from spreading.

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