A national case-control study of risk factors for listeriosis in Australia.

Listeriosis is a foodborne disease associated with significant mortality. This study attempts to identify risk factors for sporadic listeriosis in Australia. Information on underlying illnesses was obtained from cases' treating doctors and other risk factors were elicited from the patient or a surrogate. We attempted to recruit two controls per case matched on age and primary underlying immune condition. Between November 2001 and December 2004 we recruited 136 cases and 97 controls. Of perinatal cases, living in a household where a language other than English was spoken was the main risk factor associated with listeriosis (OR 11·3, 95% CI 1·5-undefined). Of non-perinatal cases we identified the following risk factors for listeriosis: prior hospitalization (OR 4·3, 95% CI 1·0-18·3), use of gastric acid inhibitors (OR 9·4, 95% CI 2·4-37·4), and consumption of camembert (OR 4·7, 95% CI 1·1-20·6). Forty percent of cases with prior hospitalization were exposed to high-risk foods during hospitalization.