Reducing the incidence of listeriosis from contaminated food has significant social health benefits, but reduction requires the use of additional or higher quality inputs at higher costs. We estimate the impact of three inputs in a food processing plant on the prevalence of L. monocytogenes contaminated finished cold smoked salmon. These three inputs were non-contamination of the raw fish fillets, non-contamination of the plant environment, and rate of glove changes on workers. We then estimate the levels of these inputs to use such that the marginal cost of these inputs become equal to the increased social health benefit of reduction in human listeriosis. Since the costs of these inputs are borne by the food processing plant, which may not be able to secure a higher product price because of asymmetric information, we show how social sub-optimal use of these inputs may result.