A case-control study was conducted from 1 January to 31 May 2003 to identify risk factors for
S. Heidelberg infection in Canada. Controls were pair-matched by age group and telephone exchange to 95 cases. Exposures in the 7 days before illness/interview were assessed using multivariate conditional logistic regression. Consumption of home-prepared chicken nuggets and/or strips [matched odds ratio (mOR) 4·0, 95% confidence interval (CI) 1·4–13·8], and undercooked eggs (mOR 7·5, 95% CI 1·5–75·5) increased the risk of illness. Exposure to a farm setting lowered the risk (mOR 0·22, 95% CI 0·03–1·00). The population-attributable fraction associated with chicken nuggets/strips was 34% and with undercooked eggs was 16%. One-third of study participants did not perceive, handle or prepare chicken nuggets and strips as high-risk products, although the majority of the products on the Canadian market are raw. These findings have prompted changes in product-labelling policy and consumer education.