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Tracking an Outbreak: The Disparities and Challenges

There have been a number of outbreaks and clusters of illnesses in the last several months, some of which have tracked back to certain foods and some that have not. In late October this year, CDC announced its investigation of a multistate outbreak of Listeria monocytogenes infections which has, thus far, led to the hospitalization of 10 people and one death. Those who became ill reported having eaten Italian-style meats both pre-packaged and in-store deli-sliced, however, no specific source has yet been determined.

Prior to this outbreak, we saw several multistate outbreaks occurring this summer with illnesses beginning in June and ranging for at least a couple of months. While the source food was determined and recalls conducted for two of those, the others remain under investigation with no identified vehicle.

  • Outbreak of Salmonella Enteritidis Infections. Reported illnesses range from June 29 to August 27. Of the 90 reported illnesses, there were 28 hospitalizations and no deaths. Epidemiologic and traceback evidence indicated peaches packed or supplied by Prima Wawona or Wawona Packing Company to be the likely source, and the company conducted a recall on August 22. As of October 16, CDC reported the outbreak as appearing to be over.
  • Outbreak of Salmonella Newport Infections. Illnesses range from June 19 to September 11. Of 705 reported illnesses, 167 were hospitalized and there were no deaths. Epidemiologic and traceback evidence showed that red onions from Thomson International Inc. were the likely source of the outbreak with other onion types also likely to be contaminated because they were grown and harvested together. Thomson recalled all red, yellow, white, and sweet yellow onions on August 1, and CDC declared the outbreak as appearing to be over on October 8.
  • Two (or three?) Outbreaks of E. coli O157:H7 Illnesses In October, FDA reported that there had been two E. coli outbreaks, for which it does not know the source but has “ seen similar recurring, emerging or persistent strains of E. coli in recent outbreaks.” One of the two outbreaks is being caused by a strain of E. coli that is genetically related to that which caused the 2019 outbreak linked to romaine grown in the Salinas region; to date, 23 cases and no deaths have been reported. The second is being caused by an E. coli strain that is genetically related to a larger, diverse genetic cluster including the strain that caused the 2018 STEC outbreak linked to romaine and environmental isolates from the Yuma growing region. To date, 21 cases and one death have been reported. TAG has heard that a third cluster of E. coli O157:H7 is also under investigation that does not match either of the other two.

Why the disparity between the outbreaks? Why are some vehicles and specific companies able to be identified and recalled, and others not? Why are some investigations conducted and finalized within a matter of months (e.g., the peach and onion outbreaks), while others lag on and sometimes never reach a complete conclusion?

That is the million-dollar question! While the answer (for many outbreaks) is simple: implementation of a single, linked, industry-wide field-to-fork, quick-access traceability system; the means of getting there is anything but.

As is evidenced by the many attempts to incorporate such a system, there are numerous challenges – beginning with the consumer to determine exactly what was eaten when, that caused the foodborne illness. Then tracing that backwards (and sideways) to attempt to determine, not only the exact food item/ingredient, but its origination and complete chain of uses. It becomes even more difficult with a pathogen such as Listeria for which symptom onset does not begin until 1 to 4 weeks after consumption of the contaminated food. For example … Quick, what did you eat yesterday? All last week? All last month (including condiments, sides, and mid-morning snack)? And what were the brands, store/restaurant where purchased, date purchased

Or consider a produce E. coli foodborne illness. While onset is generally faster 3 to 10 days after ingestion, you may attribute nausea, cramping, and diarrhea to a flu or virus going around. The most severe consequence of E. coli O157:H7 infection, hemolytic uremic syndrome (HUS), doesn’t usually begin until the diarrhea is improving, and the first signs may go relatively unnoticed. So, by the time the person, visits their doctor, is hospitalized, and the infection diagnosed, it can be a matter of weeks. And the originating produce is long past its short shelf life and no longer available for testing.

FDA’s recently proposed Traceability Rule will, hopefully, have some impact and increase traceability. But it is not the full answer — in part, because FDA’s authority was limited by Congress in its writing of FSMA: FDA cannot prescribe specific technologies or require a facility to have duplicate records or change business systems. Nor can it require “a record of the complete previous distribution history of the food from the point of origin of such food; records of recipients of a food beyond the immediate subsequent recipient of such food; or product tracking to the case level.”

With FDA essentially held to the same tracking requirements as those of the 2002 Bioterrorism Act: one forward/one back, it remains up to the industry to go beyond the letter of the law and work together to meet the challenges to mitigate, if not eliminate, the impacts of pathogenic contamination of food.


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