Multistate outbreak of listeriosis linked to Turkey deli meat and subsequent changes in US regulatory policy

Background. Listeriosis, a life-threatening foodborne illness caused by Listeria monocytogenes, affects similar to 2500 Americans annually. Between July and October 2002, an uncommon strain of L. monocytogenes caused an outbreak of listeriosis in 9 states. Methods. We conducted case finding, a case-control study, and traceback and microbiological investigations to determine the extent and source of the outbreak and to propose control measures. Case patients were infected with the outbreak strain of L. monocytogenes between July and November 2002 in 9 states, and control patients were infected with different L. monocytogenes strains. Outcome measures included food exposure associated with outbreak strain infection and source of the implicated food. Results. Fifty-four case patients were identified; 8 died, and 3 pregnant women had fetal deaths. The case-control study included 38 case patients and 53 control patients. Case patients consumed turkey deli meat much more frequently than did control patients (P=.008 by Wilcoxon rank-sum test). In the 4 weeks before illness, 55% of case patients had eaten deli turkey breast more than 1-2 times, compared with 28% of control patients ( odds ratio, 4.5; 95% confidence interval, 1.3-17.1). Investigation of turkey deli meat eaten by case patients led to several turkey processing plants. The outbreak strain was found in the environment of 1 processing plant and in turkey products from a second. Together, the processing plants recalled 130 million pounds of products. Following the outbreak, the US Department of Agriculture's Food Safety and Inspection Service issued new regulations outlining a L. monocytogenes control and testing program for ready-to-eat meat and poultry processing plants. Conclusions. Turkey deli meat was the source of a large multistate outbreak of listeriosis. Investigation of this outbreak helped guide policy changes designed to prevent future L. monocytogenes contamination of ready-to-eat meat and poultry products.