This paper describes the epidemiological and microbiological aspects of the largest outbreak of Vero cytotoxin-producing Escherichia coli O157 (VTEC O157) infection in a hospital setting in which the route of transmission was foodborne. The outbreak, which was caused by a relatively uncommon phage type of VTEC O157, occurred in four geriatric continuing care wards in May 1997. The total number of people found to be excreting the organism was 37, of whom 16 were inpatients and 11 were staff. Twelve people displayed enteric symptoms. In addition, all but two of 10 cases identified in the local community were thought to be associated with the outbreak. An epidemiological investigation amongst the hospital patients revealed a statistically significant association between VTEC O157 infection and attendance at a concert party on the continuing care wards on 17 May 1997 (relative risk = 3.22;P= 0.006). There was an even stronger relationship between consumption of home-baked cream-filled cakes brought to that party and evidence of infection (relative risk = 19.35;P= 0.00002). Further investigations in the local community, coupled with microbiological evidence, supported the epidemiological finding that homemade cream cakes brought into the hospital were the vehicle of infection for the outbreak. There was no secondary spread within the hospital. The outbreak serves as a reminder of the hazard posed by foodstuffs brought into a hospital from outside.
Copyright 2001 The Hospital Infection Society.