An outbreak of E-coli 0157 infection with evidence of spread from animals to man through contamination of a private water supply

An outbreak of E, coil O157 infection occurred in the Highland Region of Sc otland in the summer of 1999. The source of the outbreak was traced to an u ntreated private water supply. All six cases identified arose in visitors t o the area, and most had very limited exposure to the contaminated water. P ermanent residents on the same supply were unaffected. The E, coli O157 iso lates from the water, sheep faeces collected from around the source and the human stool samples were indistinguishable using pulsed held gel electroph oresis. Previously reported outbreaks of E. coli O157 linked to potable wat er supplies have resulted from structural or treatment failures, which allo wed faecal contamination of source water. Here, contamination of the water supply and subsequent human infection was due to the use of an untreated, u nprotected private water source in a rural area where animals grazed freely .