Minnesota tactics helped reveal Salmonella source

Jul 24, 2008 (CIDRAP News) – New details emerged today about breaks in the Salmonella investigation that led to the identification of the outbreak strain in a jalapeno pepper, as the number of cases in the nationwide outbreak rose to 1,284.

In past updates, the US Centers for Disease Control and Prevention (CDC) has said the emergence of case clusters—groups of patients who had the same food exposure—led its investigators to place jalapeno peppers on a list of produce items that might have played a role in the outbreak. Then on Jul 21, the Food and Drug Administration (FDA) announced that case-cluster findings led to the discovery of a jalapeno sample from a McAllen, Tex., distributor that matched the outbreak strain.

The CDC said investigators have focused on three large clusters, one of which appears to be in Minnesota, according to reports today from the Associated Press (AP) and the Minneapolis Star Tribune. In the AP report, David Acheson, MD, the FDA's associate commissioner for foods, declined to call Minnesota's findings the "key cluster," but said the data helped federal officials narrow the investigation.

Toward the end of June, officials from the Minnesota Department of Health (MDH) first became aware that several patients who had eaten at the same restaurant were sickened by the Salmonella strain blamed for the national outbreak, according to the Star Tribune's report today. Kirk Smith, supervisor of the MDH Foodborne Disease Unit, told the paper that he called on a specialized MDH group nicknamed "Team Diarrhea" to conduct case-control studies. Team Diarrhea is made up of graduate students from the University of Minnesota School of Public Health, the Star Tribune reported.

An MDH epidemiologist used credit card receipts from the unnamed restaurant to determine what the people who didn't get sick had eaten and analyzed the ingredients the restaurant used, according to the AP report. The investigation found that the manager had already switched tomato suppliers based on the FDA's Salmonella advisory, which shifted suspicion to a garnish made of diced jalapenos and red peppers, the AP report said.

Smith told the AP, "This is not like a sprig of parsley on the edge of your plate. This was sprinkled directly on almost every entrée." He said many of the restaurant patrons who were interviewed didn't notice the jalapenos, but did mention tomatoes. "Recall, that's what makes it tricky. That's why I wonder about all those initial cases [in other states]," he said.

By Jul 3, Ben Miller, trace-back coordinator with the Minnesota Department of Agriculture, had completed an investigation that identified suppliers, distributors, and farms that were the source of the jalapenos served at the restaurant where the Minnesota patients had eaten, according to the Star Tribune.

Smith told the Star Tribune that aside from "Team Diarrhea" and speedy investigators, other factors helped Minnesota officials quickly zero on an outbreak suspect:

  • Centralization of investigation activities at the state level rather than county or local levels
  • The availability of a sophisticated laboratory
  • Willingness to pursue the trace-back trail beyond state borders

Federal officials have not ruled out tomatoes as a possible source of some of the illnesses, particularly those that occurred earlier in the outbreak, which continues and has now gone on for more than 2 months. However, in mid July they started to look more closely at other possible sources, including hot peppers, and on Jul 21—based on finding the positive sample—they advised consumers to avoid eating raw jalapeno peppers and products that contain them.

Meanwhile, the CDC said today that the outbreak has increased to 1,284 patients from 43 states, the District of Columbia, and Canada, who were sickened by the relatively rare Salmonella enterica Saintpaul strain. The latest reported onset date is Jul 6. At least 239 patients were hospitalized, and officials said two deaths were possibly linked to the outbreak.

In other developments, Congress has scheduled at least two hearings to explore produce contamination issues and learn more about the difficulties federal officials have encountered during the outbreak investigation.

On Jul 30 at 1:30 pm EST the House Subcommittee on Horticulture and Organic Agriculture will explore the legal and technical capacities to do full trace-backs on fresh produce. The next day at 10 am the House Subcommittee on Oversight and Investigations will hold a hearing on lessons learned from the Salmonella outbreak and its consequences for public health. Both hearings will be available on live Web videocasts.

See also:

Jul 24 CDC Salmonella update

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