As of March 2, 2010, the Centers for Disease Control and Prevention (CDC) counted a total of 245 individuals infected with the outbreak strain of Salmonella Montevideo in 44 states. Among the 2,500 serotypes of Salmonella, according to the CDC, Montevideo is in the top 10 most common serotypes.
Because the main Salmonella Montevideo outbreak is so common in the United States, public health investigators had an extremely difficult time detecting the source of the outbreak. However, during its investigation, CDC employed a unique and novel technique that enabled it to trace the source of the bacteria–shopper cards used across the country by millions of Americans.
Initially, CDC and public health officials were able to identify a possible source by conducting a study comparing foods eaten by 41 ill and 41 well persons. The results suggested salami as a possible source of illness, with data showing ill persons were significantly more likely to eat salami than well persons in the days before they became ill (58% v. 16%).
From there, investigators sought permission from customers to track their grocery purchases using shopper cards, and then asked supermarkets and grocery stores about specific buying information. The trail led them to Daniele International Inc., a Rhode Island-based company manufacturing and distributing Italian-style salami (salame).
Soon after, on January 23, 2010, Daniele recalled about 1.3 million pounds of the ready-to-eat meats. Daniele suspected the pepper it used to season the recalled salami was also a potential source, and directed the FDA to two suppliers in New York and New Jersey. Both companies have since recalled some products.
Although the FDA is still working to identify the specific products or ingredients that became contaminated and how the contamination occurred, the use of shopper cards to trace an outbreak marks an important food safety breakthrough and a potentially valuable tool in the future.
Some state and local health agencies have used shopper cards in the past to trace contaminated food, and although the CDC had tried it a few times, never before were shopper cards used to this degree of success.
According to the CDC, private parties were extremely helpful in the investigation. Ill persons immediately gave permission for public health officials to retrieve purchase information based on shopper card numbers, and many supermarkets, including Costco, worked closely with the CDC to track down products.
CDC and its public health partners, including the Food Safety and Inspection Service (FSIS) and the Food and Drug Administration (FDA), are continuing the investigation to verify that the outbreak is controlled.