Effect Measure

As the tomato Salmonella outbreak heads past the 800 case level, it’s time to ask some questions about why we don’t know the source of what is the largest produce associated disease outbreak on record. CDC has its own explanation, namely, that figuring out where tomatoes come from and where they go is much harder than they thought. Said another way, the experts in foodborne disease outbreaks at CDC and FDA didn’t know much about the industry. Since tomatoes have been a frequent cause of Salmonella outbreaks, that seems odd, except that my experience with CDC in recent years is that it is full of inexperienced people who don’t know what they are doing being managed by incompetent managers who spend too much time brown nosing the boss who spends too much of her time sucking up to the Bush administration. Because of bad management the professional expertise at what was once the jewel in the crown of federal public health headed for the exits as soon as their twenty years were up. There are still some terrific, dedicated scientists at CDC, but they are being submerged by mediocrity and bureaucracy. But back to tomatoes:

Frustrated federal officials today reported they were still hunting for a major break in their investigation of a nationwide Salmonella outbreak thought to be caused by tomatoes, and for the first time they hinted that another type of produce might be responsible for the illnesses, which have now risen to 810 confirmed cases.

David Acheson, MD, associate commissioner for foods at the US Food and Drug Administration (FDA), at a press briefing today said teams of investigators have spent the past week taking hundreds of samples from farms, packing houses, and distributors in Florida and Mexico.

Of about 1,700 samples collected so far–mostly of tomatoes–none have yielded the relatively rare Salmonella enterica Saintpaul strain found in the sick patients, he said. (Lisa Schnirring and Robert Roos, CIDRAP News)

They’ve spent the past week taking samples? Let’s hope this doesn’t mean they didn’t take any samples until last week. Since they haven’t found any tomatoes with Salmonella yet, how sure are they tomatoes are the vehicle. The evidence for this is based on old fashioned “shoe leather epidemiology,” in this case by taking histories from the cases to see if there is a food item consumed by cases not consumed by people like them who didn’t get sick. That’s called a case – control study. Once raw tomatoes, some of it in fresh salsa or guacamole, were implicated the task was to find out where the tomatoes came from. The best way to do that is to compare the sources of tomatoes eaten by cases with those eaten by controls. Not only do you expect meals of cases to have tomatoes more often but you expect them to come from different sources. Unfortunately the FDA did not do this. They have only been trying to trace back the tomatoes from the cases, not the health controls.

Dr. Michael Osterholm, director of the University of Minnesota Center for Infectious Disease Research and Policy, also thinks that FDA and CDC have done a poor job of using independent food industry experts to help. That’s one reason why they didn’t know that tomatoes from Florida could be packed and distributed from Mexico and vice versa. The investigation field personnel are too often inexperienced, so it’s taken them weeks to figure this out, weeks during which the epidemiological trail is growing cold. That trail can be very difficult to follow even under the best of circumstances, but we are far from having the best of circumstances:

Public health authority rests with state and local departments, Osterholm said, and he acknowledged that federal officials often don’t have the authority to assign outbreak response a higher priority. He said communication between state and local health departments and federal public health officials is often poor and that states vary widely in their ability to conduct and quickly report laboratory tests. “We have a very fragmented system with major delays. For time-sensitive outbreaks, you can’t have that happen,” he said.

“The overall system is broken,” Osterholm said. “It looks like we’re doing a lot, but I want to know how many cases we’ve prevented–a very small percentage, I would argue.” (CIDRAP News)

So we’ve got broken agencies working in a broken system. That’s what you get when you cut taxes, divert money to pay for a foreign policy debacle, and run the government like a patronage shop. There’s always been some patronage and politics in federal public health (although not very much), but the last seven years are qualitatively different than any Democratic or Republican administration in recent memory. As of today there are 202 more days left in the Bush administration. You can do a lot more damage in 202 days, and the amount of damage already done is prodigious. We are so much less safe, in almost every way, after seven years of these clowns. Throw the bums out.


  1. #1 Marissa
    July 1, 2008

    Sounds like to me these guys need to go back to school. I agree. What happened to interviewing the population? Best clues are there. If it’s done half-assed you’ll end up on a wild goose chase. granted this exercise is always a tough one, but less harder than trying to track down cancer cluster cases, right, Revere?

  2. #2 Dylan
    July 1, 2008

    I suggest that we have the people currently in charge of conducting the war against Iraq assume the responsibility of determining the source of the Salmonella outbreak; while those who have yet to discover the source of the Salmonella contamination be immediately tasked with finding the solution to extracting us from the Iraq quagmire, with a method that guarantees that we flee with a program that includes “peace with honor,” and ensures that the lives of those who were lost, or broken, are given the respect that they are entitled to. In their monumental incompetence, it appears that the various elements of this Administration are almost entirely fungible.

  3. #3 Clark
    July 1, 2008

    My understanding is that a big problem is a long period of underfunding for the FDA. You could blame the Republicans for much of that (and deserveredly so) except that there hasn’t been a huge turn around the past two years. The FDA created new ways of tracking food but that system, long overdue, has been ill funded, was only approved something like six months ago, etc.

    I’m all for blaming Bush’s tendency to put people in places of authority where they have no qualifications. I think he earned that criticism. But at least a big a problem if not the main problem has been Congressional and Senatorial oversight and funding.

  4. #4 revere
    July 1, 2008

    Clark: From 1994 to 2006 we’ve also had a Republican Congress. If Bush had wanted to do something in this area they would have done it. He didn’t and they didn’t.

  5. #5 Julian
    July 1, 2008

    Jeez, these guys could have done a better job if they’d watched an episode of Threshold from the sound of it. Considering that the Bush admin started driving off the talented and the dedicated throughout the federal bureaucracy, it’s sadly not surprising that they did it at the CDC as well.

  6. #6 M. Randolph Kruger
    July 1, 2008

    And now every bacterial outbreak in my toilet is going to be blamed on Bush. It will be after he is gone too…. The Democrats are aware of this problem as Revere has posted that it was 2006 that they left control in the hands of two of the biggest idiots in US history…Harry Reid and Nancy Pelosi. First thing they did was not stop funding the war, increased the funding for it, then signed on to the new FISA bill. Nancy wanted her own 747 too and that was a priority item as well. Come to think of it they didnt approve more funding for CDC or FDA. Now is that politics or are they happy too with the way things are working out?

    Doesnt matter though, we got Bush to Bash and rightly or wrongly vilified he is outta there in January. Revere and others in an off handed way seems to indicate that things couldnt be worse…Wanna bet? Salmonella in tomatoes? What if its not an accident at all folks because its now in 36 states. Never been that high of an incidence level before. Not sure how its going to play out but there has to be something other than tomatoes causing something this big. Or its the vast GWB conspiracy that has driven off the ROADies in the federal government that were just biding their timef. Cant be anything other than that because Salmonella is a Republican disease.

    Give me a break.

  7. #7 Clark Goble
    July 1, 2008

    Revere, you miss my point. I acknowledged that. The question is why it still hasn’t changed.

    My view, at the moment, is a pox on both the Republicans and Democrats. Bush is so bad most Democrats aren’t even running to reform government (and look how little the current congress has done to reform earmarks, ethics, etc.)

    I agree with Kruger – Democrats think they can just bash Bush and people will somehow forget that they aren’t doing anything. That might even work for the next two years. But it’ll catch up with them just as it did the Republicans who went from reformers to the corrupted in an awfully short time.

    Now I will say this. Despite having stated programs to do better tracking the FDA has not made formal requests to congress for several of these programs. Having said that though they are still woefully funded and since 9/11 have been asked to do more with less. Simply blaming Bush isn’t sufficient – just like Republicans thought they could get away with blaming Clinton and talking up Patriotism and terrorism and hoping we’d ignore what they were actually doing.

  8. #8 Johnson Harvey
    July 1, 2008

    Yeah, lets blame Bush for rotten tomatoes. I bet Karl Rove is out there spiking the salsa with menacing bacteria to poison Democratic voters before November. Hate and invective are out of control in this country.

  9. #9 stogoe
    July 1, 2008

    Kruger, have you been paying attention to anything at all in the past seven years? I find it hard to believe that anyone with even a modicum of awareness of the world outside their skull would still support the war criminal monstrosity that has been the Supreme-Court-appointed fascist theocracy heckuva-job infrastructure-decimating Cheney Puppet administration.

    No, I’m not particularly happy with the Democratic Party or the cowards in Congress. But it’s trivially easy to see that they’re at least ten thousand times better than the party who’s actively trying to destroy America by any means possible – the Republicans.

  10. #10 revere
    July 2, 2008

    Clark, Johnson: The Congress is not trying (since 2006) to reform food safety and they have a bill in the works (Rosa DeLauro and Bart Stupak). So trying to blame the Democratic Congress is not valid. They’ve done a lot to lay the groundwork in the 18 months they’ve been there. This is a Bush/Republican mess. There are a lot of Bush Dog Democrats, too, and we need to replace them.

  11. #11 AJS
    July 2, 2008

    Salmonella in tomatoes?!

    According to vegan propaganda, that’s impossible as only m**t and dairy produce can support food poisoning bacteria.

  12. #12 joel
    July 2, 2008

    When I got my MPH one of the classes (Food and waterborne diseases) included a presentation of the regulatory system. The chart of federal agencies that have some role in food/water regulation was amazing. I didn’t know there were fonts that small. As you say Revere – broken agencies in a broken system. The problem is, every time something large like this shows up the response is to create a new, independent agency to monitor that problem, and you end up with too many groups and no one knowing who is actually supposed to do anything. When the garden is overgrown a little pruning is in order. In addition to a regime change we need to cut back some of the agencies and turn their functions over to a suitably powered FDA.

  13. #13 EPIguy
    July 2, 2008

    The political debate has definitely derailed this discussion. Regardless of who’s in charge, we have been practicing epidemiology in this country since the constitution was signed. This is not the first large scale food outbreak we have investigated. First, is it a surprise that there have been no environmental positives identified? When was the last time we got positive environmentals prior to having uncovered the true nature of the outbreak; few and far between. Does needle in a haystack sound like a good analogy? While FDA is far understaffed, underfunded, undermanaged, whatever, you have missed the boat on their true failures. Their main function is the prevention of further disease (what a new concept for public health), whether it have been through PSAs or a stop sale of the implicated item; in that regard I feel they failed, considering we have had 100s of new cases with incubation periods well after the initial implication of the tomatoes. It falls on the states to conduct the investigations with the coordination of the CDC. It never dawned on any state to do I case control? I doubt it. Whether they communicated those findings to the CDC/FDA is another story (another new concept: communication). Ultimately, this latest change in the investigation has caused the FDA to loose face again; remember downed cows and pig brain encephalitis…this is the third strike in recent times. The scariest part is this; what if this was a deliberate act, or better yet, what if this was something else? Maybe this will cause bureaucrats to recognize how vulnerable our food supply is….nothing like a large-scale outbreak to result in a large-scale influx of new funding. Hmmmm…that kinda makes you wonder……

  14. #14 M. Randolph Kruger
    July 2, 2008

    AH HA! EpiGuy gets it. Biggest Salmonella outbreak in US history…Coincidence or is it terrorism? Cant find the source because there may not be one… It could be a concerted effort in a multi state shipping region to Salmonella bomb the food supply. You have 36 states with their guys on it too so WTF is happening here?

    And indeed its a states problem, not so much the FDA if you look at the regulatory hierarchy. States like their cake and to eat it too. Kind of like disaster response in Louisiana.

  15. #15 revere
    July 2, 2008

    Randy: Yes, we all forgot to look under the bed for the Salmonella. Enough about that. About whose responsibility. The tomatoes cross state lines. They are involved in interstate commerce. Regulating them falls under the Commerce Clause of the Constitution. The idea that Minnesota will regulate beef from Nebraska is ridiculous and it doesn’t work that way.

  16. #16 M. Randolph Kruger
    July 2, 2008

    Oh you are right Revere, and those tomatoes might not be the cause at all. They might actually be getting salted with Salmonella.

    Might interest you to know that the FBI is now taking a look at shippers and tomatoes, peppers and a whole slew of stuff. Epi has this one right. Why havent we banned the sale of the affected veggies? Fraid to piss of the Mexicans? That is a function of the FDA and I would start there as he said. Cant get it if you dont eat it. The source hasnt been determined and quite frankly just saying tomatoes and Bush isnt going to cut it this time around. There are some serious indications that this is no accident. Poor mans bioweapon? We already know that Al Qaeda is operating in Venezuela and that their operatives are in Mexico.

    Besides, how do you do surveillance on tomatoes when it can exist inside of the veg?

    Its all conjecture of course and I wont give the Bush Administration any cover if its found to be a lapse. But its a jurisdictional nightmare, will create yet another bureacracy loaded with ROADies that do no work and just move paper around. These outbreaks have happened as far back as I can remember…..Not this big though and that is the concern.

  17. #17 Oldfart
    July 3, 2008

    I fail to understand how 800 cases is BIG.
    10,000 might be BIG.
    I fail to understand why Kruger thinks our enemies expect to destroy us by infecting 800 random people with Salmonella.

    I do not fail to understand the failures of 12 years of Repugnant control of either Congress or the White House or both. However, is this really the end of the world as we know it?

  18. #18 revere
    July 3, 2008

    Oldfart: This is big in a different sense. It is a huge multistate outbreak of a single bug, demonstrating how widely an upstream contamination can be spread. So on one level it is a commentary on our food distribution system and its vulnerabilities. On yet another level it is a red flag about the state of food safety protection. Maybe you can’t prevent everything, but when you see something happening to find you are powerless to figure out what is going on or what to tell people. It shows the system is broken, as Mike Osterholm said.

  19. #19 M. Randolph Kruger
    July 3, 2008

    OldF-You might not understand that this outbreak might not be circumstantial or bad surveillance. Its a states issue for the better part until as Revere says its clear that a criminal or trans-state or border issue comes to light. There are probably other cases that were not reported because they just simply went to their doctors, took the Kao and/or vomited the stuff up. I had it once via some beef and its not pretty.

    Yarking it up quickly, a day long fever and a healthy system will clear it. Some people would call it the non-existent intestinal flu. 800 cases and counting and 36 states. They cant find the source. So there is a qualified mind set that without a source, this was intentional. Dry run for ingestion anthrax? That my friend if it gets into the food supply would be far more than 10,000. You put it into your system and well, its like 90% fatal. Those that would make it would be screwed up for years if not permanently.

    Now you may not call 800 big. I would and do as it does pose a lot of questions about food surveillance that we are supposed to be paying for and not getting. Thats my reference to the ROADies above. We would put idiots in charge who would lateral from one government job into this new bureaucracy. Thats how our government system works and its one of the reasons the Gerberdinator took them out in the CDC. But its different with their ROADies there. They are lazy, they are scientists, they are quirky but ….they are smart when something like this comes along. FDA? Its administration only. Thats about all they do until you end up with Thalidamide babies…administrate. Then they regulate.

    Revere is partially right here and neither he or I could say that this was preventable. I do now know that the Chinese are pissed because their veggies are rotting on the dock from all of the inspections that they are sending in. They are trying to send it FOB shipping point and the buyers aint having it here. So it comes in, and rots.

    The system is broken? I cant see that we ever had one. How many times has it ever been interdicted? None that I could pull up.

    Lets hope that it is some source rather than terrorist, else we are going to be getting nutz again. Poison the food supply and its the targeting of civilians. Use of bio is by declaration that has been in place for some forty years and that is that we will respond in kind….

  20. #20 Steve
    July 3, 2008

    “The best way to [identify the implicated tomatoes] is to compare the sources of tomatoes eaten by cases with those eaten by controls. Not only do you expect meals of cases to have tomatoes more often but you expect them to come from different sources. Unfortunately the FDA did not do this.”

    A methodological question here: how will tracing the source of tomatoes eaten by people who didn’t get sick help identify the responsible tomatoes? If a case-control study identifies that tomatoes are associated with disease, then the cases will necessarily have substantially more exposure to tomatoes than the control group. If the tomato traceback is performed for both groups and tomatoes eaten by some controls are from the same source as those eaten by cases, does this invalidate the observation that most cases ate a particular kind of tomatoes? On the other hand, if the traceback reveals that the two groups ate tomatoes from different sources, does this really provide new evidence supporting the observed association? Does anybody really see the failure to trace the tomatoes eaten by the control group as a big methodological error?

  21. #21 M. Randolph Kruger
    July 3, 2008

    Steve, thats not correct. The controls you are suggesting are the problem. There are too many cases popping up with no direct point to this place as the source. Cross contamination has been ruled out so far. So where is it coming from? No one knows because there are few links if any that put this tomato patch in relation to a produce house. Very diverse areas hit all at the same time is what we are talking about here. Its not as simple as you think and I provide no cover for FDA except to say that in this as the states didnt call it until several had mulitple cases. CDC didnt get involved until the numbers were in the tens.

    I can tell you though that they are looking at the concentration of the salmonella in individual tomatoes to see they were helped out a bit by someone or multiple someones. There is no common link so far that anyone has been able to determine.

  22. #22 revere
    July 3, 2008

    Steve: Nothing has been ruled out. Cross contamination somewhere in the chain is still the leading suspect. The idea behind trace backs for control tomatoes is to try to get a handle on the source by looking at the differences between tomatoes that made people sick compared to those that didn’t.

  23. #23 Steve
    July 4, 2008

    MRK and revere:

    My question is a methodological one that can be divorced from the current Salmonella Saintpaul outbreak. I will try to restate the question more generically:

    Imagine that a case-control study identifies bananas as being associated with disease. Among the cases who ate bananas, say that 80% of them ate bananas that trace back to Farm A. If we do not perform trace backs on the bananas eaten by the control group, we will conclude that Farm A is the source of the problem.

    Let’s now pretend that trace back is performed on the controls, as is being suggested. Please consider a few scenarios for the trace back of the control group bananas (remembering that controls have substantially less exposure to bananas in the first place):

    In scenario 1, 80% of the control group bananas also trace back to Farm A. The fact that bananas are associated with disease has not changed. Can we draw any conclusions about Farm A as the source of the problematic bananas that are different than the conclusions we drew when we only new trace back information for the cases? Do we now conclude that Farm A is not the source of the bananas? If we conclude that Farm A is not the source, what do we do next to try and find the true source?

    In scenario 2, only 20% of the control group bananas trace back to Farm A. Is this additional evidence implicating Farm A?

    What if 50% of case bananas and 50% of control bananas traced back to Farm A? What do we conclude?

    How big a percentage difference between the case and control tracebacks do we need in order to change our original assessment that Farm A was the source?

    Given Dr. Osterholm’s qualifications and that I only have a humble MPH, I am surely missing something here, but for the life of me I can not see how the trace back of controls will actually inform our conclusions about the source. The idea seems to have common sense merit, but, upon further reflection, I’m not sure it works out in the end.

  24. #24 M. Randolph Kruger
    July 4, 2008

    You are talking epidemiology Steve. We got a briefing on this yesterday and it wasnt encouraging. I dont think they have a clue where its coming from because it wasnt at any farm A. They did find some traces of it, but nothing conclusive and certainly not 800 cases worth in 37 states. There would have to be cross contamination of a huge scale to get it to that scale. It could lead back into Mexico where there are no regulations at all. I guess that if you worked it right you could load a spray bottle with it and shotgun a case or two at a time? I dont know if it will stick around long enough to infect someone or what the level has to reach before sickness occurs. I mean is there a diff between the level of ingested infection and how sick you get? Revere might have the answer to that one or not. I asked our EMA guy to check and nothing has come back yet.

    You probably heard that the tomatoes might have been shipped to Mexico from Florida and then back out to the US too. So far…nothing. No warehouses, no farm A,B or C kind of thing. So far that is. This is whats so mind boggling about it. All other outbreaks in the past were detected, then determined to be at your farm A and then at warehouse B and contaminating truck C. Generally they got it in under three weeks. Never, ever has there been an outbreak this big in so many states. Flaky or paranoid? You be the judge.

    Deliberate contamination? Lets hope not.

  25. #25 revere
    July 4, 2008

    Steve: You have raised several issues. Let’s not deal with the statistical ones (how big a difference do you have to have), since that takes a longer explanation and I will do that in a series of posts. Let’s just deal with your question on the logic of study design. The trace back problem is not really different logically than the etiology problem. There the question was, “What’s different about what the cases ate than the controls?” The trace back question now becomes, “What’s different about the case tomatoes compared to the control tomatoes?” If we were sure it was a question about what farm it came from than we might get away with just a case traceback (although a simultaneous case-control traceback would still be quicker and more efficient since it would reveal a difference more quickly). In this case we don’t even know what feature of the tomato origins to look for so having the control tomato origins would have been really helpful. Remember, the FDA and CDC staff knew hardly anything about tomato production and were learning it in the field, so the comparison info would have revealed what was “normal” and what wasn’t. It is also the way these things should be done. Experienced investigators would do it that way. These guys didn’t.

    The basic idea here is to use data to reveal what is going on. Control traceback would have provided more information more quickly.

  26. #26 Steve
    July 4, 2008

    Thanks for trying to explain it, revere. One of the nagging concerns I have with doing traceback on the control-group tomatoes is that you are only examining a subset of the controls. Because you are selecting this subset based on their having been exposed to the very exposure associated with disease, this subset must be relatively small relative to the entire control group. If the control group was selected randomly, that “randomness” has now been lost. If the entire control group was matched, then the subset is no longer matched. Given that a large proportion of Salmonella cases (maybe 30 to 1) are sub-clinical, and we are now specifically selecting a subset of the control group based on their having the same exposure that we think caused disease, aren’t we essentially maximizing the possibility of miscategorizing the disease status of the people in the subset? If so, we should have little confidence that any subtle differences observed when comparing the exposures of the cases to the exposures of the control subset are meaningful. The original case-control study was specifically designed to identify the exposure associated with disease, not to parse the distribution pathways of tomatoes.

  27. #27 revere
    July 4, 2008

    Steve: I think a better way to look at the traceback portion (versus the etiological portion) is that it is a case control study of tomatoes, not people. The incriminated tomatoes are the cases and the non-incriminated tomatoes are the controls. What’s different about them? I don’t think this is a sampling issue. In an outbreak the cases are not assumed to be a random sample of the cases, although the controls are assumed to represent the population from which the cases arose. But rather than worry about the statistics here, concentrate on the underlying logic. What’s different about the origin of the case tomatoes versus the non-case tomatoes? That’s what provides the clues about origin.

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