• Giardia infection occurs worldwide. Groups at high risk include infants, young children, international adoptees, travelers, immunocompromised individuals, and patients with cystic fibrosis.

  • Transmission of infectious Giardia cysts to humans may occur via 3 routes: waterborne, fecal-oral, or foodborne.

  • Giardiasis is especially common in areas with poor sanitary conditions and limited water-treatment facilities.

  • Symptoms of acute giardiasis include diarrhea, malaise, and abdominal cramps. Chronic giardiasis can result in significant weight loss, while acquired lactose intolerance occurs in up to 40% of patients.

  • Antigen and nucleic acid detection tests are more sensitive than stool microscopy.

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