Disease determinants of sporadic salmonellosis in four northern California counties. A case-control study of older children and adults.

A population-based, case-control study of sporadic salmonellosis was conducted in 1988 and 1989 in four northern California counties. The study included 120 patients and 265 control subjects. Conditional logistic regression analysis (adjusted for age) revealed that patients were more likely to consume undercooked chicken prior to the onset of disease (odds ratio [OR], 23.57; 95% confidence interval [CI], 2.89 to 192.30). Elevated associations were also found with recent travel to foreign countries (OR, 9.69; 95% CI, 3.18 to 29.56), diabetes (OR, 6.29; 95% CI, 1.56 to 25.34), hormonal replacement therapy (principally conjugated estrogen) in older women (OR, 4.20; 95% CI, 1.82 to 9.71), and antibiotic therapy prior to illness (OR, 1.96; 95% CI, 0.86 to 4.37). The problems of studying self-selected cases that may lead to alternative explanations for these findings are also discussed.