Special Edition IX — Salmonella Saintpaul Outbreak…Concerns About FDA/CDC
Trace Back The Control Group
Jim Prevor’s Perishable Pundit, July 3, 2008
One hope for solving this problem and clarifying the cause of this outbreak came out in the FDA/CDC’s recent conference call. It was good news to learn that CDC was basically starting anew and doing new survey work with people who became ill after June 1, 2008. This survey work would involve additional questions and presumably build on learning from inadequacies in the initial investigation of those who fell ill in April and May.
Right now there are 179 people who say they fell ill in June, and this number will presumably increase as more reports come in.
What was shocking — and very disappointing for the produce industry — was word that even in this new investigation, CDC is not doing any traceback of the control group. This group consists of people similar in demographics to the ill people but who did not fall ill.
Our interview with Michael T. Osterholm PhD, M.P.H., focused on the necessity for doing traceback with the control group. Here is what Dr. Osterholm said:
…it is not biologically plausible to have Mexico and Florida both at the source of this outbreak. It epitomizes the ineptitude of the investigation. FDA and CDC should have obtained tomato product consumption information from both outbreak cases and controls. They needed to conduct full fledged tracebacks all the way back to the source not only of the sick cases but of the control group as well.
The epidemiology conducted to learn what product is associated with this outbreak by interviewing those sick and those not sick on what they were eating is a prerequisite but the epidemiology needed to go further. It was critical for the investigators to learn the locations of where both the cases and controls ate tomatoes and trace back from there.
When doing the traceback, you may come up with a few possibilities of where the tomatoes came from. If you collect data over time of the cases and controls, using the same methods to make the product association, you may find 85 percent of outbreak cases trace back to a certain field or grower, or re-packer versus the control product. Then you begin to get a much better handle on where product came from.
Q: Why did the government forego this strategy?
A: FDA and CDC have not made this a priority. They will never find a silver bullet by just tracing back a product. They’re looking for a cluster that matches up exactly with the one gun barrel. They’re under the false impression that they’re going to get a clean, clear-cut answer by finding the magic cluster. They need to do this case/control approach.
Now whatever happened with the initial investigation, whatever judgments or considerations were made, this much is beyond dispute: It didn’t work.
A quote attributed to Albert Einstein defined insanity as doing the same thing over and over again yet expecting different results. So surely CDC should be open to enhancing its methodology. Certainly there is no way that doing a traceback on the control group could hurt.
We have Dr. Osterholm, a highly credible person with extensive experience, saying this is a necessity. This is from a man who was doing traceback in Salmonella investigations on tomatoes a decade ago.
So, we have a methodology that has not been working, a highly credible source suggesting a specific improvement in that methodology, yet when asked, CDC gave a simple response of no, it is not tracing back the control group.
This should be a major concern for the produce trade associations, which should be requesting that CDC add this to their methodology right now, while it still can, so that this post-June 1, 2008 survey will be more productive and more likely to produce an answer as to the source of the salmonella.
This CDC also needs to consider its dismissive manner. An issue such as this merits an explanation. In light of the failure of the last traceback and the input from Dr. Osterholm, if CDC doesn’t want to do a traceback on the control group, it should have the decency to explain why to the general public.
Does CDC lack the resources required? Does it have a substantive disagreement with Dr. Osterholm?
The people at CDC are hired by the citizens of America to handle this portion of their affairs. A decent respect for the people who pay the bills requires CDC to be more transparent in its decision-making process..