Use of global trade item numbers in the investigation of a Salmonella newport outbreak associated with blueberries in Minnesota, 2010

In August 2010, the Minnesota Department of Agriculture and Minnesota Department of Health investigated an outbreak of six cases of Salmonella Newport infection occurring in northwestern Minnesota, which identified fresh blueberries as the cause. Initially, traditional traceback methods involving the review of invoices and bills of lading were used to attempt to identify the source of the outbreak. When these methods failed, novel traceback methods were used. Specifically, supplier-specific 12-digit Global Trade Item Numbers (GTINs) and shopper-card information were used to identify a single blueberry grower linked to cases, corroborating the results of a case-control study in which consuming fresh blueberries was statistically associated with illness (5 of 5 cases versus 8 of 19 controls, matched odds ratio [MOR] undefined, P = 0.02). Consuming fresh blueberries from retailer A was also statistically associated with illness (3 of 3 cases versus 3 of 18 controls, MOR undefined, P=0.03). Based on initially incomplete evidence in this investigation, the invoices pointed to wholesaler A and grower A, based on first-in-first-out product rotation. However, when point-of-sale data were analyzed and linked to shopper-card information, a common GTIN was identified. This information led to an on-site record evaluation at retailer A, and the discovery of additional records at this location documented the supply chain from grower B to wholesaler C to retailer A, shifting the focus of the investigation from grower A to grower B. This investigation demonstrates the emerging concepts of Critical Tracking Events (CTEs) and Key Data Elements (KDE) related to food product tracing. The use of these shopper-cased data and the event data that were queried by investigators demonstrates the potential utility of consciously designed CTEs and KDEs at critical points in the supply chain to better facilitate product tracing.