Laboratory confirmation of infection with/without symptoms from stool, duodenal fluid, or small bowel biopsy specimen:
- Demonstration of Giardia lamblia OR
- Demonstration of Giardia lamblia antigen OR
- Detection of Giardia lamblia by PCR
Clinical illness in a person who is epidemiologically linked to a confirmed case.
Clinical illness is characterized by diarrhea, abdominal cramps, bloating, weight loss, or malabsorption.