Abstract
In August 2004 seven cases of Escherichia coli O157 infection were identified in children on holiday in Cornwall, southwest England, all of whom had stayed at different sites in the area. Isolates from all seven cases were confirmed as E. coli serogroup O157 phage type 21/28. We carried out a case-control study among holidaymakers who visited the beach. A standardised questionnaire was administered by telephone to parents. They were asked where on the beach the children had played, whether they had had contact with the stream that flowed across the beach, and about their use of food outlets and sources of food eaten. Cases were more likely to have played in the stream than controls (OR [1.72- undefined]). The time spent in the stream by cases was twice spent there by controls. Cases and controls were equally exposed to other suspected risk factors. PFGE profiles for all the cases were indistinguishable. Increased numbers of coliforms were found in the stream prior to the outbreak. Cattle were found grazing upstream. We suggest that the vehicle of infection for an outbreak of acute gastrointestinal illness caused by E. coli O157 was a contaminated freshwater stream flowing across a seaside beach. The onset dates were consistent with a point source. Heavy rainfall in the days preceding the outbreak might have lead to faeces from the cattle potentially contaminated by E. coli O157 contaminating the stream, thereby leading to the outbreak. Control measures included fencing off the part of the stream in which children played, and putting up warning signs around the beach.
Highlights
Human infection with verocytotoxic Escherichia coli O157:H7 (E. coli O157) is associated with clinical illness ranging from non-bloody diarrhoea to haemolytic uraemic syndrome (HUS) and death
We suggest that the vehicle of infection for an outbreak of acute gastrointestinal illness caused by E. coli O157 was a contaminated freshwater stream flowing across a seaside beach
Three potential sources of sewage contamination from overflow drains around the stream were discovered upstream. This investigation supports the hypothesis that the vehicle of infection for an outbreak of acute gastrointestinal illness caused by E. coli O157 was a contaminated freshwater stream flowing across a seaside beach in Cornwall
Summary
Human infection with verocytotoxic Escherichia coli O157:H7 (E. coli O157) is associated with clinical illness ranging from non-bloody diarrhoea to haemolytic uraemic syndrome (HUS) and death. It is the most common cause of renal failure in children [1,2]. The pulsed field gel electrophoresis (PFGE) profiles for all the isolates were indistinguishable Prior to this there had been no clustering of this phage type in the area. We carried out a case-control study to search for supportive evidence that the stream or other exposure was the vehicle of infection in this outbreak of E. coli serogroup O157 phage type 21/28
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