Giardiasis - Fact Sheet


What is giardiasis?
Giardiasis is an intestinal illness caused by a one-cell parasite called Giardia lamblia. It is a fairly common cause of diarrhea. Cases may occur as a single case, in clusters, or in outbreaks.

Where are Giardia parasites found?
Giardia parasites are found in infected people (with or without symptoms) and wild or domestic animals including pets such as dogs and cats. Beavers have gained attention as a potential source of Giardia contamination of lakes, reservoirs, and streams.

How does this parasite spread?
The Giardia parasite is passed in the stool of an infected person or animal and may contaminate water or food. Ingesting the parasite may cause illness. Person-to-person transmission may also occur in households, day care centers, or other settings where hand-washing practices are poor.

Who gets giardiasis?
Anyone can get giardiasis, but it tends to occur more often in people in institutional settings, people in day care centers, parents of infected children, foreign travelers, and individuals who consume improperly treated surface water

What are the symptoms of giardiasis?
People exposed to Giardia may experience mild or severe diarrhea, cramps, bloating, excessive amounts of gas in the stomach; in some instances no symptoms may be present. Occasionally, some people will have chronic diarrhea over several weeks or months, with significant weight loss. Fever is rarely present.

How soon do symptoms appear?
The symptoms appear 1 – 2 weeks after exposure (average 7 days).

How long can an infected person carry the Giardia parasite?
A person can shed the parasite in stool throughout the entire period of infection, from weeks to months.

Should an infected person be excluded from work or school?
People with active diarrhea (e.g., infants, young children, certain handicapped individuals) may need to be excluded from settings such as day care, and occupations such as food handling or direct patient care, until they no longer have diarrhea.

What is the treatment for giardiasis?
Several prescription drugs are available to treat a Giardia infection. Treatment of carriers without symptoms is generally not recommended. Some individuals may recover on their own, without medication.

How can giardiasis be prevented?
Some important preventive measures include:

  • Carefully wash hands thoroughly after toilet visits and before eating or handling food.
  • Wash hands after every diaper change, especially if you work with diaper-aged children, even if you are wearing gloves.
  • Avoid consuming water from recreational use areas (e.g., rivers, lakes, ponds) and improperly treated drinking water.
  • Avoid sexual practices that involve possible contact with stool.



This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.


For additional information on this disease, visit the Centers for Disease Control and Prevention website.







To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.