Giardia Infection (Giardiasis)

Giardiasis is an intestinal infection caused by a microscopic parasite called Giardia. This parasite lives all over the world, especially in bodies of water. If you accidentally swallow it, it takes up residence in your small intestine and multiplies, feeding off the nutrients there. This can cause a variety of intestinal symptoms, including foul-smelling diarrhea, bloating and gas, stomach cramps, nausea and fatigue.

Giardiasis symptoms can be mild to severe, and some people never have symptoms. The infection typically clears by itself after a few weeks, but people with weaker immune systems may have a harder time clearing it. A healthcare provider can prescribe antiparasitic medications for giardiasis if you need them. Sometimes, people continue to have symptoms for weeks to months after the infection has gone.

How common is giardiasis?

Giardiasis is common throughout the world. It’s the most common parasite infection in the U.S., where it affects over a million people each year. In developed countries in general, it affects an estimated 10% of the population. In developing countries, giardiasis affects an estimated one-third of the population.

Giardia thrives in regions and environments with less public sanitation, especially in natural bodies of water and inadequately sanitized public water supplies. Children are more often infected than adults, especially those under the age of 4. In the U.S., childcare centers are a frequent source of outbreaks.