We developed a risk assessment of human salmonellosis associated with consumption of al-falfa sprouts in the United States to evaluate the public health impact of applying treatments to seeds (0–5-log 10 reduction in Salmonella) and testing spent irrigation water (SIW) during production. The risk model considered variability and uncertainty in Salmonella contamina- tion in seeds, Salmonella growth and spread during sprout production, sprout consumption, and Salmonella dose response. Based on an estimated prevalence of 2.35% for 6.8 kg seed batches and without interventions, the model predicted 76,600 (95% confidence interval (CI) 15,400 – 248,000) cases/year. Risk reduction (by 5 – to 7-fold) predicted from a 1-log 10 seed treatment alone was comparable to SIW testing alone, and each additional 1-log 10 seed treat- ment was predicted to provide a greater risk reduction than SIW testing. A 3-log 10 or a 5-log 10 seed treatment reduced the predicted cases/year to 139 (95% CI 33 – 448) or 1.4 (95% CI < 1 – 4.5), respectively. Combined with SIW testing, a 3-log 10 or 5-log 10 seed treatment reduced the cases/year to 45 (95% CI 10–146) or < 1 (95% CI < 1 – 1.5), respectively. If the SIW cover- age was less complete (i.e., less representative), a smaller risk reduction was predicted, e.g., a combined 3-log 10 seed treatment and SIW testing with 20% coverage resulted in an estimated 92 (95% CI 22 – 298) cases/year. Analysis of alternative scenarios using different assumptions for key model inputs showed that the predicted relative risk reductions are robust. This risk assessment provides a comprehensive approach for evaluating the public health impact of various interventions in a sprout production system.
