A school waterborne outbreak involving both Shigella sonnei and Entamoeba histolytica

In an outbreak of gastroenteritis affecting 730 students, Shigella sonnei a nd Entamoeba histolytica were isolated from the stool specimens of patients . Environmental investigations revealed the source of infection to be conta mination of underground well water by sewage from a toilet. The outbreak en ded with the closure of the well water supply. To avoid such problems, inst itutions and other groups that maintain their own wells, including schools and summer camps, need to be vigilant about maintenance and check for poten tial contamination.