Brainerd diarrhea is a syndrome that is characterized by acute onset of watery diarrhea with 3 or more loose stools per day and experiencing typically around 10 to 20 episodes per day of explosive watery diarrhea with urgency and fecal incontinence and this can last up to 4 weeks or more. This syndrome is named after the place where the first outbreak occurred in 1983 in Brainerd, Minnesota. Despite numerous research and investigation, the cause of Brainerd diarrhea is still not identified. Today, it is known to occur in sporadic cases and outbreaks.
Since 1983, there have been seven cases reported of Brainerd diarrhea outbreaks with the six cases that occurred in the United States, in which five are from rural settings and one on a South American cruise ship based in the Galapagos Islands. The first outbreak was considered as the largest outbreak that involved 122 persons. In this first outbreak, raw or unpasteurized milk was suspected as the primary cause for the transmission of the disease. For the outbreak in the Galapagos islands and Henderson County, Illinois which affected 58 and 72 people respectively, contaminated and inadequately chlorinated or unboiled water was suspected to be the cause of Brainerd diarrhea. Drinking untreated well water in Henderson County caused illnesses but people who boiled the same well water before drinking did not get sick. However, these are only implications and were not proven to be the cause of the disease but it was also thought that Brainerd diarrhea does not spread contagiously from one person to another.
The primary root cause of Brainerd diarrhea is still not known. At first, it was thought to be an infectious agent such as parasites and bacteria but examinations for parasitic, bacterial and viral pathogens were unsuccessful, leaving a possibility that Brainerd diarrhea may be caused by a chemical toxin. Such toxin has not yet been found.
