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1997 Case Definition

CSTE Position Statement(s)

  • 09-ID-34

Clinical Description

An illness caused by the protozoan Giardia lamblia and characterized by diarrhea, abdominal cramps, bloating, weight loss, or malabsorption. Infected persons may be asymptomatic.

Laboratory Criteria for Diagnosis

  • Demonstration of G. lamblia cysts in stool, OR
  • Demonstration of G. lamblia trophozoites in stool, duodenal fluid, or small-bowel biopsy, OR
  • Demonstration of G. lamblia antigen in stool by a specific immunodiagnostic test (e.g., enzyme-linked immunosorbent assay)

Case Classification


A clinically compatible case that is epidemiologically linked to a confirmed case


A case that is laboratory confirmed


The 1997 case definition appearing on this page was re-published in the 2001 CSTE position statement 2001-ID-08 and the 2009 CSTE position statement 09-ID-34.1 Thus, the 1997, 2002, and 2010 versions of the case definition are identical.


  1. CDC. (1997). Case Definitions for Infectious Conditions Under Public Health Surveillance. MMWR, 46(RR-10), 1-55.