pepperssalmonella.jpgGovernments’ foodborne disease investigating agencies (CDC, FDA, USDA-FSIS, and the many state, local, and tribal units) are not infallible, but yesterday’s release in the New England Journal of Medicine of a collaborative study on the 2008 Salmonella Peppers outbreak is not nearly the indictment of the methods and conclusions of that outbreak that United Fresh Produce Assocation said it was today.  In truth, the lessons to be taken from the outbreak, and the mistaken identification of tomatoes as the culprit, lie just as heavily with the produce industry.

One confounding factor in many outbreaks–something that inhibits the rapid identification of the contaminated food item–is products that are widely consumed amongst all ages and populations, particularly when the contaminated product is so heavily contaminated that it causes illnesses in nearly every state in the country.  Moreover, when the product is peppers that are very rarely a menu item in themselves, but are instead used as only one ingredient in many extremely common food items (and often in appetizers like salsa that people sometimes forget about in recounting their meal), that identification problem is exacerbated even further. 

This outbreak was identified in late May, and immediately many top epidemiological units in the country (many were members of the ten state FoodNet group) jumped into the investigation.  From what the journal article and study say, in depth case control studies were undertaken in a separate but coordinated fashion in several different geographic regions nationally. 

The problem was neither the work, the people doing it, or the methods they were using.  It was that they were dealing with some extremely difficult epidemiological circumstances, and were further inhibited by not only the commonality of the product (and the problem that poses with traceback efforts once a suspect item is identified), but also the fact that the industry was only marginally helpful in being able to trace their products all the way back to the source.  This is important not only because full traceback inhibits further shipment of the contaminated product, but also because finding a suspect product that came from a single source is a major epidemiological point that suggests that the suspect product might be the right one. 

Here is what an in depth read of the article, rather than latching onto a misstep in the process that, admittedly, had serious consequences for the tomato industry, will reveal:

Environmental assessments conducted as part of the epidemiologic investigations of nine restaurant clusters did not identify recent diarrheal illness among food handlers. A total of 12 tracebacks of raw Roma and red, round tomatoes were completed: 8 tracebacks from 7 sporadic cases and 4 tracebacks from restaurant clusters. These tracebacks did not converge on any one geographic location, grower, or supplier. All tomato tracebacks included sources from Mexico, Florida, or both. Environmental investigations were conducted at five farms or packing firms in Mexico and three in Florida. Only one firm was packing tomatoes in Mexico at the time of the investigation, and all farms in Mexico and Florida had finished harvesting. The FDA analyses of approximately 183 domestic and imported tomato samples and 113 environmental swabs from tomato operations in Florida and Mexico did not identify salmonella.

Tracebacks to farms from 13 restaurant clusters were completed for jalapeño peppers from five states, including 3 restaurants (cluster D, consisting of two restaurant locations, and cluster G) in which jalapeño peppers were implicated. All 13 tracebacks led to distributors in Texas and Mexico that received jalapeño peppers from Mexico. The outbreak strain was isolated from a jalapeño pepper sample obtained from a produce importer in Texas that received jalapeño peppers from a packing facility in Nuevo Leon, Mexico. The traceback from the packing facility was complex, with commingling of products and a network of interrelated distribution points.

The FDA investigated two farms in Mexico (Farm A and Farm B) that supplied peppers to the packing facility (Figure 2). Traceback records identified other farms that also supplied the facility during this period. Farm A, which grew Roma tomatoes in addition to jalapeño and serrano peppers, harvested all three crops between late April and late July and was an indirect supplier to the packing facility. Farm B supplied the same packing facility both through direct shipments and also indirectly through distributors. Farm B, located approximately 100 miles from Farm A, was this packing facility’s main pepper supplier. Agricultural water samples from Farm A yielded salmonella but not the outbreak strain. The FDA did not collect tomatoes at Farm A. The outbreak strain was isolated from two environmental samples, agricultural water, and serrano peppers on Farm B, which grew jalapeño peppers and serrano peppers, but not tomatoes, and harvested produce from mid-April to mid-June. The Colorado Department of Public Health and Environment isolated the outbreak strain from a jalapeño pepper collected from the home of a case subject in Colorado and traced this pepper from the grocery store where it had been purchased to another distributor in Texas. The source of these jalapeño peppers was not determined.

United Fresh CEO Tom Stenzel had the following to say:

“The study in this week’s New England Journal of Medicine underscores the fact that temporal associations based on memories of what someone has eaten weeks earlier can be useful, but not definitive, in these investigations. It’s clear from the study that many sick individuals recalled eating a salsa product, but failed to recognize the peppers that were contained as an ingredient. By prematurely jumping to the conclusion that tomatoes were causing the outbreak, officials may have unwittingly allowed the outbreak to continue.”

The reality is that the peppers outbreak was tough.  It caused 1,500 people to fall ill with confirmed infections, maybe 50,000 to fall ill with unconfirmed illnesses, and caused at least two deaths.  The government isn’t to blame for these consequences; not even close.  Mistakes may have been made in the process of identifying peppers, but under the circumstances, I doubt very seriously that those mistakes were due to inattention or incompetence.  More likely the hypothesis generation during the outbreak was just incredibly complex.  It may have been easier if the produce industry did a better job in delivering the full traceability that it knows it needs to, or in preventing the contamination in the first place.