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Brainerd Diarrhea

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Clinical Features

Profuse and chronic watery diarrhea typically associated with urgency and incontinence that begins acutely and lasts from 2-36 months.

Etiologic Agent



An estimated 5,000-8,000 patients with chronic diarrhea clinically similar to Brainerd diarrhea are cared for by U.S. gastroenterologists each year. Approximately every 3 years, CDC investigates an outbreak of Brainerd diarrhea affecting 50-100 people.


No known sequelae; however, many people suffer adverse psychologic consequences related to the long duration of an incapacitating illness.


Untreated water has been implicated in several outbreaks and unpasteurized cow's milk has been implicated in one.

Risk Groups

The elderly appear to be at greatest risk for Brainerd diarrhea, although several cases among children and young adults have been described.


No surveillance system exists for Brainerd diarrhea or for other chronic diarrheal syndromes of unknown etiology (e.g., collagenous colitis, microscopic colitis).


Data are insufficient to indicate an increase or decrease in incidence.


Despite numerous intensive laboratory investigations, the etiologic agent of Brainerd diarrhea remains a mystery. Histologic criteria for distinguishing Brainerd diarrhea from other chronic diarrheal syndromes were developed from outbreak-related specimens, but need to be evaluated in specimens from patients with sporadic cases of chronic idiopathic secretory diarrhea.


Newer techniques, such as ribosomal RNA amplification on sterile site tissue biopsies may shed new light on the etiologic agent. The histologic criteria can be tested against specimens from a recent outbreak.

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