Epidemiology and Infection

Temporal and geographical distributions of reported cases of Escherichia coli O157[ratio]H7 infection in Ontario

P. MICHEL a1c1, J. B. WILSON a1a3, S. W. MARTIN a1, R. C. CLARKE a2, S. A. McEWEN a1 and C. L. GYLES a4
a1 Department of Population Medicine, Ontario Veterinary College (OVC), University of Guelph, Guelph, Ontario, Canada
a2 Guelph Laboratory, Health Canada, Guelph, Ontario, Canada
a3 Laboratory Centre for Disease Control (LCDC), Health Canada, Ottawa, Ontario, Canada
a4 Department of Pathobiology, Ontario Veterinary College (OVC), University of Guelph, Ontario, Canada


The distribution of 3001 cases of verocytotoxigenic Escherichia coli (VTEC) reported in the Province of Ontario, Canada, were examined to describe the magnitude of this condition geographically and to evaluate the spatial relationship between livestock density and human VTEC incidence using a Geographical Information System. Incidence of VTEC cases had a marked seasonal pattern with peaks in July. Areas with a relatively high incidence of VTEC cases were situated predominantly in areas of mixed agriculture. Spatial models indicated that cattle density had a positive and significant association with VTEC incidence of reported cases (P=0·000). An elevated risk of VTEC infection in a rural population could be associated with living in areas with high cattle density. Results of this study suggested that the importance of contact with cattle and the consumption of contaminated well water or locally produced food products may have been previously underestimated as risk factors for this condition.

(Accepted November 20 1998)

c1 Author for correspondence: Dr Pascal Michel, Guelph Laboratory, Health Canada, 110 Stone Road West, Guelph, Ontario, Canada, N1G-3W4.