Where It Comes From
Feces from infected people or animals that contaminate drinking water, private wells, and recreational water; hardy cysts survive for weeks in cool water and resist some chlorine.[1][3]
How You Are Exposed
Swallowing contaminated water or ice; eating unsafe food; touching contaminated surfaces or people (childcare) and then your mouth; sexual practices involving oral–anal contact.[1][2]
Why It Matters
Causes diarrhea, gas, stomach cramps, nausea, fatigue; can be prolonged and cause malabsorption and weight loss.[1][2]
Who Is at Risk
Young children, childcare workers, travelers to areas with unsafe water, hikers/campers who drink untreated water, and people with weakened immune systems.[1][2][4]
How to Lower Your Exposure
Wash hands with soap and water; don’t swallow pool or lake water; drink treated water—boil 1 minute (3 minutes at high altitudes), or use 1‑micron (cyst‑rated) filters or UV; maintain pools; practice safer sex.[1][2][3]
References
- [1]CDC. Giardia (Giardiasis) — About. https://www.cdc.gov/parasites/giardia/
- [2]CDC. Giardia — Prevention & Control. https://www.cdc.gov/parasites/giardia/prevent.html
- [3]EPA. Giardia and Drinking Water. https://www.epa.gov/ground-water-and-drinking-water/giardia-and-drinking-water
- [4]WHO. Guidelines for Drinking-water Quality (protozoa: Giardia/Cryptosporidium). https://www.who.int/publications/i/item/9789241549950