Effect Measure

Trust is not transitive, as someone recently pointed out, when reporting on the airline pilot who carried a gun into the cockpit and then accidentally or negligently discharged it and blew a hole in the plane. We had every reason to trust the pilot to be able to fly a 747, but not necessarily to handle a firearm properly. Trust isn’t transitive.

There is no doubt that Yi Guan, a professor at the University of Hong Kong, is an expert on H5N1 virus, its genetic lineages and surveillance for the virus in wild birds. He has reportedly screened, via cloacal swabs and fecal specimens, more than 200,000 wild and free ranging aquatic birds and poultry in China since 2000. So if he has an opinion about whether proper surveillance can stop a pandemic it is reasonable to listen to what he says and consider it seriously. But it is not necessarily reasonable to trust his judgment because he is an expert at the lab bench in using surveillance specimens. Because once Guan talks about a pandemic he is talking about a global scale outbreak of disease in human beings. That involves epidemilogy. So I am slightly skeptical of a pronouncement by someone whose speciality is surveillance of birds, not the epidemiology of influenza in people:

“For disease control, surveillance must be a long term effort. You know where it is and you know it is coming, like a spark of fire you can extinguish it,” Guan said.

“If not for all this surveillance and detection ability, the pandemic would probably have already come.”

Drawing from what is known of past pandemics, Guan believes that surveillance and strict control measures are the answers.

“Pandemics don’t happen suddenly, they have an early phase, mature phase, outbreak phase. The virus changes step by step, it takes a long cooking time,” he said.

“If a virus gets into humans in the early phase, the transmission ability is very low. At most, they infect their families, but it can’t go further into the community.

“This phase is the golden point to control. Once it matures and becomes (efficient in) human-to-human (transmission), it will be too late.” (Tan Ee Lyn, Reuters)

My own view, as an epidemiologist, is that this proposition is highly unlikely. Even in Guan’s specialty, we know very little about the movement of the virus. How does it get from one place to another? What is the role of poultry movement versus wild birds? (What are the routes of poultry movement and how do we follow and control them? What are the migratory routes of wild birds? (We only know this in very broad generalities, not at the even fairly coarse resolution that we need to control the virus if birds are a mode of movement, numerous maps, notwithstanding; you will find these maps are based on scant information and many inferences, insufficient for what would be required to really know and understand bird movements globally). Nor is surveillance for the virus complete, effective or comprehensive. That’s just for starters.

There’s also the question of human epidemiology. At the molecular level we don’t know what makes the virus transmissible (we have clues, only) or virulent (still only clues) or pathogenic (still more clues). In humans we still aren’t sure of the relative importance of different modes of transmission (large or small droplets, fomites, possible undiscovered animate vectors). Where does the virus hang out in nature? Are their additional reservoirs besides poultry and wild birds? What accounts for the seasonality? Where does the virus go in the “off season”?

Even taking Guan’s conjecture in its strongest possible form, that we know enough about these missing data points to say that stopping a pandemic was possible through surveillance alone, there are the obvious questions about public health in the Real World. Public and veterinary health are grossly under supported and things are getting worse, not better. The international system that supports cooperation between countries cannot even make the half century old influenza virus surveillance system work, much less impose the kind of interference in “national sovereignty” that would be required to snuff out an incipient pandemic even if we knew it was coming. What surveillance can do is warn us to get ready, not be the firewall that prevents the invasion.

Yi Guan is a genuine expert in the virology of H5N1 and an expert in the Art of Surveillance as we now practice it. Surveillance is of supreme importance in global preparation to face a potential pandemic with a very dangerous virus. But just because it is his opinion that the hammer he wields will hit all the nails on the head doesn’t mean that a good hammer is even close to being a sufficient tool even under the best of circumstances.

Trust isn’t transitive.


  1. #1 SusanC
    March 31, 2008

    Hear! Hear!

    Beware of the extrapolation of ‘wisdom’.

  2. #2 K
    March 31, 2008

    Excellent piece Revere

  3. #3 herman
    March 31, 2008

    We have Revere shiting on Randy only because he is a right wing fascist. But please be aware that Randy knows what he is talking about, much more than Revere, when it comes to bird flu.
    We have assholes on all continents criticizing Henry Niman. But you had better swallow that shit, and listen to what the man is saying now. We are up to our assholes in danger from birdflu now. Not 10 years from now. While you stupid shits sleep, this virus is getting ready to kick your ass now.
    Now please post, and debate whether the glass is half full or half empty. But after you do, please read Nimans post about the rat shit clusters multiplying in the shithole that is Indonesia.
    I live in Medellin Colombia, where life is cheaper than cheap. For $100 US you can pay an assasin to kill the shit out of whoever you want. Thank heavens Revere is on to of this bird flu, but I swear, if bird flu hits Colombia, we are all dead here. I am an American, and I cannot believe how messed up the government is here. They just keep their thumb up their ass, and steal whatever they can, when they are not selling cocaine. Because a friend told me they tried to kidnapp her nephew yesterday. Here, for money, you die quick and easy.
    Revere, keep your filthy paws off of Randy. You atheist bastards do not appreciate how cool it is to be a right wing fascist. But honestly I agree with Revere. Go ahead and keep firing missiles into Somalia to kill terrorists, and killing innocent people and the same time. The asshole captain that ordered the firing of that missile should rot in hell. When the oil runs out, those who control the power in the United States, who are responsible for waterboarding and firing missiles to shed innocent blood in Somalia, will meet me in hell.

  4. #4 JJackson
    March 31, 2008

    Trust is partially transitive.

    If Revere gives me advice in epidemiology I am inclined to take his word for it, if the topic is virology, histology or quite a few other ‘oligies I would still have a higher – if slightly diminished level of trust. If I was going to sail a small boat across the Pacific and he gave me tips on compass swinging and alignment I would thank him politely. My point being that confidence limits will depend on accumulated trust (has he made a lot of statements that were habitually correct), how close is his know area of expertise to the subject in question and finally how much dose it matter (‘that is a good knot’ for A] trussing this chicken or [B] attaching your parachute).
    Where I am in complete agreement with Revere is that Guan is wrong, and very badly so. It is difficult to see how someone of his eminence could not have a deeper appreciation of how his work fits into the large battle against pandemic influenza. To be that far off the mark makes me wonder if he was misquoted, misunderstood or was misunderstood.

  5. #5 Mathematician
    March 31, 2008

    Argh. People are getting the wrong idea about what transitive means. It’s nothing to do with whether

    we trust X to do Y implies we trust X to do Z

    It’s everything to do with whether

    we trust X (e.g., the pilot) and X trusts Y (e.g. his gun) implies that we trust Y.

    A relation R is transitive iff for all x, y, z,
    xRy and yRz implies xRz

    Just sayin’ 🙂

  6. #6 revere
    March 31, 2008

    mathematician: That was my thought at first. But it turns out that this is a specific use. There are many entries for it, including (I think) a wikipedia article. But you are prefectly correcct when it comes to binary relations.

  7. #7 Lea
    March 31, 2008

    Did the Yi Guan get his idea from this release on 28 March?

    Predicting the Next Major Virus
    By Anthony Ramos, Wildlife Trust New York
    posted: 28 March 2008 10:11 am ET

    In a paper published in February by the leading scientific journal Nature, scientists at the Consortium for Conservation Medicine (CCM) Wildlife Trust New York, the Zoological Society of London (ZSL), Columbia University (New York) and the University of Georgia announced a major breakthrough in the understanding of what causes diseases like HIV/AIDS and SARS to emerge, and how to further predict and prevent future devastating pandemics by plotting a global map of “Disease Hotspots.”

    (more) …….


  8. #8 AnnieRN
    March 31, 2008

    Shucks, Herman, I’d love to be able to read what you have to say, but I can’t get past your pathetic, uncreative vocabulary. I don’t want to swallow excrement, and I’m not a stupid sleeping pile of excrement, and my guess is that Revere’s parents were truly married. And, Indonesia is not really an anus, as you so pointedly stated.
    For Pete’s sake, you were supposed to be done communicating like this when you were 14.
    Excellent post, Revere.
    AnnieRN, rolling her eyes again….

  9. #9 Patch
    March 31, 2008


    I could point out the numerous inaccuracies in your post but it would be easier to concur on the accuracy of your facts. So here it goes:

    < "crickets chirping">

    You seem to switch topics more often than personalities. If you don’t like the blog, you and your personalities should start your own. You appear to have more than enough experts within your own mind to make some excellent excrement. I know that would suit me better than your posting here. When you post, I’m tempted to waste my time reading your commentary for entertainment and end up chastising myself.

  10. #10 G in INdiana
    April 1, 2008

    Herman, back away from the key board, go to the medicine cabinet and take out your medications. Ingest a double dose and go lie down for a while.
    In all the time I’ve been reading this site, that had to be one of the strangest, most disjointed posts I’ve seen.
    That aside, thank you for a most informative post, Revere.

  11. #11 victoria
    April 1, 2008

    AnieR, Patch, G in Indiana,


  12. #12 Pixie
    April 1, 2008

    From a practical point of view, there is no way that we can continue on with surveillance as we have, with no new ideas, and expect that it will stem the tide of H5N1. Why? Because H5N1 is winning. It’s clear that even pre-pandemic the methods we are using to combat it just aren’t working and reliance on them comes at a very high price.

    To carry on as we have been, as Yi Guan suggests, will simply cause too much pain, even well before any pandemic outbreak. What kind of pain? The kind of pain that they are feeling in Bangladesh:

    “The Bangladesh Poultry Industries Association (BPLA) said the deadly virus led to the closure of more than 50 percent of the farms, turning nearly five million people jobless.”


    I really respect Yi Guan’s work, and his courage, but it’s possible that lab work, as valuable as it is, can insulate a researcher a bit too well.

  13. #13 Claudia
    April 1, 2008

    Revere, I share your skepticism on this issue.
    Being an expert in one field should by no means be taken as proof that one can be an expert in another field, regardless of how related the two might seem to be.

  14. #14 M. Randolph Kruger
    April 1, 2008

    Herman-I am not a fascist by any stretch. Lets just say that I have risen to the occasion when necessary before. I doubt seriously that I know more about BF than Revere does. We are all though strangers in strange land on this stuff and what we do know is far outweighted by the dont knows on it.

    Now Victoria, Herman has been warned more than once about it and the body politic is just letting Herman know that he is off based here. Even I have said more than once he needed to review his post a bit before he send it. Revere indicates that he posts on more than one name and that is not acceptable.

    Reveres is/are smart guys. They are into the prevention of it. I am into the acceptance that it will happen and mitigation. I would truly hope that he gets to win this battle. If not, there had better be a lot of people around like me.

    Herman-You do need to tamp it back a bit old son. I spent a lot of time in the gathering of information in the military and sometimes it truly wasnt fun. Fascists are a grouping of like minded peoples.

    Call me a benign psychopath. If I get rolling there isnt much around to stop me. But as long as my button isnt pushed, I am that “He seemed to be so nice” guy that you read about in the papers after an incident. It is a unique individual trait so no, not a fascist.

    I am also a realist. Revere posts up often about how we need to do this and that in the public health arena. I agree, but only in as far as that it does need a fix. Its how we get there that we differ. His borders on socialism/communism that all people are entitled to it. I disagree. We are not entitled to anything but by our system, and promises that cannot be kept due to the costs.

    Ease up Herman. Sounds like you are truly frustrated about something…Its not Revere and his handling of me. He and I get along just fine….

    BTW Revere-Good post on Yi G. One thing though that you may have missed is that he may have information that the Chinese are not passing out. Remember the dust up when they alerted the world two years ago to the consternation of the Chinese govt? Points taken though.

  15. #15 victoria
    April 1, 2008

    Thanks Randy,

    I realised what the body politic were doing. I just found the acid vitriol very confronting, and unnecessary. There are nicer ways to ask someone to tone down their language, and you Randy, showed us the way. Thank you. Dare I say it, you are a true Southern gentleman.

  16. #16 M.Randolph Kruger
    April 1, 2008

    S. Gentleman only on demand. I can be a real SOB when I need to. Besides Herman, Revere’s might be female…. They can put their filthy paws on me if they want.

  17. #17 victoria
    April 1, 2008

    Oooooooooh,you, you, you, RUDE MAN!

  18. #18 Lea
    April 1, 2008

    And this could all be more of the Communist nations attempt to quell the fires before the Olympics and appear to be in control of the situation.

    But then again, the other wise peace loving monks, are doing a good job of bringing attention to the area.

  19. #19 M. Randolph Kruger
    April 1, 2008

    Yeah, I get that a lot Victoria.

  20. #20 AnnieRN
    April 2, 2008

    Revere, I’ve been thinking about this post since my first reading of it. I’m coming back to thank you for catching what the non-epidemiologists here probably would have missed. It’s easier to see this inappropriate “extension” of expertise in fields which don’t appear to be so closely related (e.g. human medicine and Egyptian history), but I would have missed this one entirely if you hadn’t pointed it out. Thanks! AnnieRN

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