Giardia infection (giardiasis) is one of the most common causes of waterborne disease. The parasites are found in backcountry streams and lakes but also in municipal water supplies, swimming pools, whirlpool spas and wells. Giardia infection can be transmitted through food and person-to-person contact.
Giardia parasites live in the intestines of people and animals. Before the microscopic parasites are passed in stool, they become encased within hard shells called cysts, which allows them to survive outside the intestines for months. Once inside a host, the cysts dissolve and the parasites are released.
Although anyone can pick up giardia parasites, some people are especially at risk:
- Children. Giardia infection is far more common in children than it is in adults.
- People without access to safe drinking water. Giardiasis is rampant wherever sanitation is inadequate or water isn’t safe to drink.
- People who have anal sex. Having anal sex without using a condom puts you at increased risk of giardia infection, as well as sexually transmitted infections.