We lawyers rely on information from all sources in sifting through the epidemiological evidence to make conclusions about an outbreak’s source. For information on developing food safety crises, E. coli lawyer Bill Marler’s www.marlerblog.com is rivaled only by Phyllis Entis, a microbiologist who moonlights, and daylights too I think, as an authority on pretty much everything related to food safety, and even sometimes its politics. In typically comprehensive fashion, she put together today at efoodalert a summary of all the evidence on the St. Louis-area E. coli O157:H7 outbreak linked, most likely, to an item on Schnucks salad bars–an outbreak that has all the halmarks of bad produce:
[T]he outbreak victims range in age from 1 to 94, and live in St. Louis city and four surrounding counties – St. Louis, Jefferson and St. Charles counties in Missouri, and St. Clair county in Illinois. The Illinois Department of Public Health acknowledged on October 28th that it was investigating a single illness in St. Clair County that might be linked to the Missouri outbreak.
The Missouri Department of Health and Senior Services is testing samples from an additional 25 suspect cases as part of the investigation into the outbreak, which appears to be linked to food sold from supermarket salad bars. At least some of the suspect salad bar components were supplied by distributors or processors outside of the state of Missouri, and FDA has been called in to assist in the inspection of the individual links in the distribution chain
Other points raised: stool samples from an additional 25 “suspect” cases are being tested currently, so the number ill in this E. coli outbreak may grow susbstantially. One of the suspect cases is a resident of Illinois, which makes one wonder whether the Missouri portion of this outbreak is possibly the leading edge of a larger multi-state or regional outbreak caused by a contaminated produce item that went to other retailers as well. Or maybe the Illinois case is secondary, or had recent travel to the St. Louis area, or is otherwise an outlier. And this kind of an outbreak can be tough to figure out:
The U.S. Centers for Disease Control and Prevention (CDC) has been called upon to assist in the epidemiological investigation, and is carrying out a case control study. The study will compare foods eaten by confirmed outbreak patients with foods consumed by a control group of healthy individuals living in the same area. With judicious questioning – and with some luck – the case control study might be successful in identifying one or more probable food sources for the outbreak.
Salad bar-related outbreaks can be especially difficult to trace to a source, due to the sheer number of different items present, and the potential for cross-contamination from serving utensils or the dropping of one salad bar item into another. Small salad ingredients, such as sliced vegetables, cherry tomatoes, and sprouts are especially susceptible to landing in the wrong bin. And people often don’t remember every vegetable or garnish that they selected.
Another complication in this outbreak investigation is the short shelf life of salad ingredients. The contaminated component may no longer be in the distribution chain. The longer it takes for a possible food to be identified via patient interviews and the case control study, the less likely it becomes that the contaminated food will be identified.