Effect Measure

Swine flu’s ticket to ride

If there was ever a graphic illustration of how global interconnectedness affects public health, it’s the swine flu affair. Wherever it started, the current crop of cases seems related to Mexico, either as the epicenter or via travelers. Four US states have cases. Those not on the Mexican border are related to travel to Mexico. Kansas, New York City, the suspect cases in secondary school teachers and students in Auckland, New Zealand just returned from Mexico. And France has two suspect cases also just returned from Mexico, as does Spain. We’ve discussed the problem of infectious disease on airplanes several times here (see this post). Surprisingly there are few documented cases in the medical literature (there’s a good review by Mangili and Gendreau in Lancet. 2005 Mar 12-18;365(9463):989-96). There is at least one flu outbreak in 1979 caused by turning off the ventilation system in a plane full of military recruits while it sat on the runway (Moser et al., Am J Epidemiol. 1979 Jul;110(1):1-6).

Here’s the abstract:

A jet airliner with 54 persons aboard was delayed on the ground for three hours because of engine failure during a takeoff attempt. Most passengers stayed on the airplane during the delay. Within 72 hours, 72 per cent of the passengers became ill with symptoms of cough, fever, fatigue, headache, sore throat and myalgia. One passenger, the apparent index case, was ill on the airplane, and the clinical attack rate among the others varied with the amount of time spent aboard. Virus antigenically similar to A/Texas/1/77(H3N2) was isolated from 8 of 31 passengers cultured, and 20 of 22 ill persons tested had serologic evidence of infection with this virus. The airplane ventilation system was inoperative during the delay and this may account for the high attack rate. (Moser et al., AJE)

With current air travel, no place is farther than a single incubation period for influenza. And no place is immune. While there aren’t any pig farms in Israel, there could easily be swine flu. From Haaretz:

Authorities fear a case of swine flu may have made it to Israel after a 26-year-old Israeli who just returned from a trip to Mexico checked himself into the hospital reporting flu-like symptoms.

On Sunday, the Foreign Ministry urged Israeli nationals in Mexico and certain parts of the United States to exercise caution after the deadly swine flu strain killed up to 81 people in the central American country. (Haaretz)

Forget about local containment. Forget about border controls. They’ll only make things worse. Swine flu has a ticket to ride. We should be putting all our efforts in managing the consequences.


  1. #1 paiwan
    April 26, 2009

    We would be grateful that the aircraft has installed UVC together with ventilation system. I hope that it will become mandatory to install UVC in closed transportation vehicles as far as the public health is concerned.

  2. #2 anon
    April 26, 2009

    swine don’t fly.
    Viruses of swinflu are usually strictly separated by continents/blocks, that’s why we speak of Eurasian and American swineflu.

  3. #3 anon
    April 26, 2009

    so it’s a mystery how and where they mixed this time.
    (and maybe why it took so long that this virus appeared)
    they should have tested and found that reassortment in a lab
    After all it’s still partly the evil 1918 virus.

  4. #4 Tom DVM
    April 26, 2009

    In general, because it is asymptomatic and transmissible for a relatively prolonged period of time, travel advisories and airport closures etc. have limited usefulness when it comes to preventing influenza from moving to other jurisdictions and countries.

    However, rules are made to be broken. In this case, it appears that we have a ‘mature’ virus that has already evolved into distinct subtypes…with a more aggressive form in Mexico and a less aggressive form outside Mexico.

    I think we should have immediately stopped tourist travel to Mexico, until we could prove that there was no difference in make-up between them.

    The fact that the World Health Organization did not act in a timely manner will be the beginning of the end for this counterproductive agency.

    As it is, the World Health Organization is a flawed ‘political’ entity offshoot of another flwawed political entity…certainly not ‘scientific’ or ‘regulatory’.

    The fact that they did not act will prove once and for all that the WHO is of little use or potential.

  5. #5 ellie
    April 26, 2009

    Anyone else here notice the total lack of information that has coming from Mexico in the past few days? Although there has been news of Mexican authorities ramping up containment measures, there have been no new numbers released since (I think) last Thursday. The official count is still 1,000 sick and 81 deaths. These are old numbers.

    The silence is deafening.

  6. #6 revere
    April 26, 2009

    Tom: WHO (Fukuda) is saying they are genetically identical. That’s all I know, but suggests these aren’t two subclades. There are other explanations for the difference and we’ll have to wait to see what it turns to be.

    elie: I’ll have a post up this afternoon (2 – 3 pm EST) on this topic.

  7. #7 Monotreme
    April 26, 2009

    revere, your attitude is incomprehensible to me. It is obvious that this pandemic is being spread by people flying in planes. Closing the airports would stop this spread. This is simple, common sense. Closing airports would not “make things worse”, it would prevent people from drowning in their own fluids. What on earth are you thinking?

  8. #8 Tom DVM
    April 26, 2009

    Under the ‘Kiss’ principle…it is the only explanation.

    Dr. Fukuda had better re-check his samples.

  9. #9 another
    April 26, 2009

    I wonder how many itineraries are already being cancelled due to this.

    There’s some unavoidable transcontinental travel in my near future, but the idea of spending hours sealed in a small tube packed with my fellow primates is none too appealing.

    Had the pleasure of flying to SE Asia during the 2003 SARS outbreak. Was entirely too aware of every breath. As a bonus, just as we hit the runway in Bangkok the gentleman immediately behind me sneezed with enough force for me to feel a fine mist settle on my right cheek. Not looking for a repeat of that.

    Interesting to read that the shutdown of the ventilation system was implicated in the case you cited. Reminds me of the dilemma we all face while flying: Are we better off with our individual air nozzle turned on or off?

  10. #10 Jon Schultz
    April 26, 2009

    Tom, Dr. Niman said (at FluTrackers) that he thinks there are 10,000 to 100,000 cases or more in Mexico, but the Mexican authorities are just counting or reporting the serious ones. That would explain the seeming difference at this point.

  11. #11 Dylan
    April 26, 2009

    I am watching the first few minutes of the news conference; the initial message seems to be…DON’T PANIC!!!! WE’RE NOT PANICKING…NO WE’RE NOT…AND DON’T YOU PANIC, EITHER!!!! AHHHHHHHHHH!!!!!!

  12. #12 Tom DVM
    April 26, 2009


    If you remember, that was an argument used in the past regarding H5N1.

    Dr. Niman may or may not be right…it has yet to be confirmed. I don’t think so.

    The critical thing here is that if the WHO has gambled wrong…they have just allowed a virus with a potential greater than the Spanish Flu in 1918 to escape.

  13. #13 Jon Schultz
    April 26, 2009

    Tom, I can’t comment on the wisdom of border closings but for accuracy here’s what Dr. Niman said:

    “In Mexico they are only counting pneumonia cases. There are probably 10-100X that number of mild cases, so there are 10,000 to 100,000 cases in Mexico (maybe more).

    The numbers in the US are fewer, so the pneumonia and deaths have not appeared yet.”

    That’s at:

  14. #14 Houston
    April 26, 2009

    My post was erased, anyway
    don’t panick if you get intestinal flu

  15. #15 Dylan
    April 26, 2009

    An astonishingly ignorant press person just asked whether the President had been vaccinated with oseltamiver or zanamiver, yet. I swear, it’s true! AHHHHHHHHHHHHHH!!!!!!

  16. #16 James Bowery
    April 26, 2009

    “Forget about border controls. They’ll only make things worse.”

    Cut out the value judgments.

  17. #17 revere
    April 26, 2009

    Lots of questions and I can’t do them all at this point (which means they’ll likely slip through the cracks as the thread scrolls, so apologies in advance).

    Tom: genetic variants are not the only explanation or even the most likely given the evidence. Others hae been discussed here already.

    mono: We agree my position is incomprehensible to you. Let me try to explain it to see if we can get over it, so at least even if you disagree, you will comprehend it. Closing air travel is a draconian measure with no good evidence of the extent of benefit. But one can see immediately some of the problems. When you stop air travel you also disrupt in a major fashion the movement of goods and services and people. Many of them are things that will need to be moved around to service infrastructure, do public health, keep the economy going, etc. The effect of that means this is far from a no brainer. So the balance which seems so clear to you isn’t clear to many people, even most people in public health as far as I know (although I haven’t taken a poll, the subject has been much discussed).

    Regarding estimates of how many cases there are in Mexico, mild or serious, no one knows because there is no way to estimate them at the moment. While some people may guess at some numbers, they are just guesses. I’m not going to guess about this. If pressed I guess there were a lot of unrecognized cases. How many? I don’t know.

    Closing the border is fruitless. We are trying to have a closed border now. We don’t have one. It is porous as can be and we can’t prevent that. Nor would it likely make much difference. This cat is out of the bag.

  18. #18 Tom DVM
    April 26, 2009


    I don’t mean to belabour the point /:0)…but we heard the same type of arguments when we were in the early stages of H5N1 in Asia, and specifically in Vietnam.

    Many expers at the time were saying that the only reason patients were dying, was because the cases were occuring in Third World countries with poor healthcare systems diets, pollution etc.

    Later, we came to realize that treatments in Vietnam were equivalent to or better than treatment in Western Countries…and the argument fell away.

    Now we are saying that the reason persons are dying in Mexico is because it is a less developed country with poor healthcare, diet, pollution etc.

    If I am right and the causation is the most likely…two unique viruses-whatever (and it would be too early to tell if the Mexican or the American strain was more evolved)…

    ..then in retrospect..as always in these situations…the WHO has made a tragic blunder…

    …as in they had an opportunity to isolate the more virlent subtype-strain in Mexico…and since they didn’t and tourists are still travelling there, the more virulent strain producing one of the more severe pandemics, is today escaping needlessly to the rest of the world.

    They tried to isolate H5N1…it didn’t work and was never going to work…

    …and then when they have a real basis to try it in Mexico, they sit on their hands.

  19. #19 pp
    April 26, 2009

    A question from a long-time lurker re: the theory that the CFR is actually much, much lower in Mexico (because there’s perhaps tens of thousands of unreported mild cases).

    As much as I’m hopeful that’s true, how does that square with the fact that the fatalities we’ve seen have been disproportionately among healthy 20-40 year-olds? In other words, I would have assumed (not being any sort of expert but just having casually followed flublogia since I learned of the threat of H5N1 back in 2005) that a new pandemic might follow one of two possible patterns:

    (1) A relatively mild illness, which (like seasonal influenza) disproportionately kills (relatively small numbers) of the very young, very old, and immunocompromised; or

    (2) A severe illness (like H1N1 in 1918, or like a potential worst-case H5N1 mutation) which disproportionately kills healthy young adults — perhaps due to cytokine storm.

    But wouldn’t it be sort of strange if (as Niman’s supposition might suggest) it’s a relatively mild illness in most — but isn’t particularly fatal for the usual victims of seasonal influenza — but then for some reason IS particularly lethal for CERTAIN healthy young adults???

    I’m not suggesting I have any sort of answers, just curious as to the thoughts of those who know much more than I do…

  20. #20 wenchacha
    April 26, 2009

    revere: It seems like the time to close the airport would have been before the Mexican cases were discovered, which is to say, impossible. The fact that we already have the porous border thing, plus Spring Breakers from at least the US and Canada makes me think that the virus has had quite a while to spread already. Now we get to learn more about the incubation period.

    I guess if I had been on one of the planes that carried people who were later discovered to be ill, I’d wish I had known beforehand, maybe to avoid infecting all my friends and family at home. If we are fortunate, the Mexican death rates will have another variable and the virus will not have high fatality rates elsewhere.

    Still, it is a reminder of our tiny Six Degrees of Kevin Bacon Planet. Get a virus that has a long incubation period plus the lethality of SARS or Ebola, and we would be frakked.

    It’s also a little concerning that we are still a ways off from the ideal H5N1 vaccine or treatment and up pops a novel virus out of thin air. If virologists felt like they were scrambling on avian flu, this must be a nightmare.

  21. #21 Monotreme
    April 26, 2009

    revere, you are wrong on basic facts. I guess what is incomprehensible to me is that you are ignorant of these things. Your response addresses two issues, science and infrastructure. Let’s address these separately. First, science.

    1. There is extensive empirical evidence that travel restrictions work. During the 1918 pandemic, America Samoa was spared the pandemic because of a strict naval quarantine. Meanwhile, the populations of nearby islands were decimated by the virus.

    2. There are published studies demonstrating that influenza viruses are transmitted to North America from Asia every year by air travel.

    3. It is freaking obvious that this virus is being transmitted by tourists to Mexico. Pick up a newspaper and read it, will you?

    Now infrastructure.

    Halting passenger travel would have prevented nearly every case in the US. What’s more important, allowing tourists to go to Mexico or stopping a pandemic? C’mon, this should be a no-brainer. For countries that don’t have any cases, there is still time for them to save themselves by halting all passenger travel.

    Re: critical supplies. I have long argued against globalisation and in favor of stockpiling for this very reason. Unfortunately, we are still dependent on supplies from other countries. However, we can acquire these with minimal risk by putting the military in charge of transporting them. If necessary, they can use their respirators and other PPE.

    Right now, Mexico is the focus. While we have some time, we should rapidly increase our stockpiles of essential goods and start working on local manufacture of anything critical.

  22. #22 James Bowery
    April 26, 2009

    Relatively self-sufficient, geographically isolated places like New Zealand had a window of opportunity that is now closed. Similar places like Iceland may still have the opportunity to protect themselves if they act now.

  23. #23 James Bowery
    April 26, 2009

    Much more investigative attention needs to be paid to this particular BBC report:

    “two of my partners who worked in this hospital (interns) were killed by this new virus in less than six days”

    Imputing a case fatality rate CFR = 2/(#interns*prevalence) where #interns is the total number of “partners” this guy has, and prevalence is the fraction (0.0 to 1.0) of the population with the flu, puts us in a dilemma: Any reasonable choice for #interns and prevalence results in a CFR much higher than the 2.5 to 5% 1918 Spanish Flu CFR.

  24. #24 phytosleuth
    April 26, 2009

    What? No phase 3? Easy. Just redesign the chart:


  25. #25 revere
    April 26, 2009

    Tom: This isn’t the same situation. The virus has been sequenced in both places. The explanation isn’t based on medical care (few of the US cases even got medical care) but on selection bias.

    mono; In case you haven’t noticed, most of the world isn’t like American Samoa. If you want historical examples there are plenty. Consider Chinatown and the plague. But you aren’t trying to convince me. You are trying to win in argument. We hae each state our cases. Shutting down air travel would be dumb. Of course people do dumb things and people argue for dumb things (consider Lou Dobbs), but that doesn’t make them smart things. I think you are arguing for something supremely dumb. You, of course, disagree.

  26. #26 Phillip Huggan
    April 26, 2009

    Revere I’m waiting on the 2pmET update 🙂
    Right now I’d suggest all shipping that has left Mexico in the last 1.5 months and not yet arrived at destination port; that those ship employees be given a cursory screening for flu symptoms by a port doctor.
    There is an argument for non-essential travel restrictions to/from Mexico as it seems all non-regional cases have come as a result of recent travel. Obviously it won’t contain the spread but it would buy time (an extra week, I dunno) to prepare (try to bring health systems up to Canadian standards as best as possible) and real-time brainstorm. If present social-distancing Mexican measures appear to be “working” when we look back two weeks from now, they can be implemented globally and the extra time bought by travel restrictions might be key. Likewise if spread continues in Mexico and more draconian measures are implemented and “work”.
    I’m not advocating non-essential Mexico travel ban as of 1pmET. There are 1000 suspected Mexico cases since Apr 13 and 1/2 of samples sent to Atlanta/Winnipeg have been positive. So 50 new cases a day is the grain of salt undercount. Once again, track down ships on high seas from Mexico.

  27. #27 Phila
    April 26, 2009

    America Samoa was spared the pandemic because of a strict naval quarantine.

    Well, I’m convinced.

  28. #28 Monotreme
    April 26, 2009

    revere, wrong again. I’m not trying to win an argument, I’m trying to save people’s lives.

    No, the whole world isn’t like a small island in the Pacific. But as James Bowery points out above, some countries are:

    1. New Zealand.
    2. Britain
    3. Ireland
    4. Iceland
    5. Greece
    6. Madagascar

    etc, etc.

    Continental areas face more of a challenge, but they can at least slow down the virus by closing their airports. That’s what empirical data suggests, which you choose to ignore.

    Discussions about a new vaccine are underway. Once the decision is made to make the vaccine, hopefully very soon, the clock starts. It will be at least 13 weeks until we have a vaccine. Every second we buy the vaccine makers, the more people who will live.

    I think your philosophy and politics are blinding you to the obvious.

  29. #29 Pork Flu
    April 26, 2009

    The swine flu virus will be deadly and catastrophic 10 miles away from our border, but when it crosses the US border it will only cause mild symptoms, so I’m not worried! Our magical border will stop all viruses from being deadly.

  30. #30 Phillip Huggan
    April 26, 2009

    To put it bluntly and honestly, no one is dying in the developed world (yet).

  31. #31 The Doctor
    April 26, 2009

    Three Possible Scenarios

    My current view is that there are three reasonable probabilities of how this outbreak may play out.

    #1: The outbreak spreads widely around to globe but self-terminates due to the onset of summer weather in the Northern Hemisphere (although the Southern Hemisphere is now entering fall!). The virus would then re-emerge in the NH fall as occurred in Sep 1918.

    #2: The virus defies the usual seasonality seen with ordinary flu and goes pandemic worldwide right away. Non-seasonality was a feature of the Spanish Flu pandemic.

    #3: The virus outbreak peaks shortly without spreading very far and simply goes away never causing a pandemic.

    Of the three, I think #1 is most likely with #2 beginning possible and #3 being most unlikely.

    If the pattern suggested in #1 does occur, what can we expect?

    The CDC has the new H1N1 sequence and is currently trying to decide how to develop it into a vaccine. Obviously, if we go the egg route, we will not get any doses before October. This will be too little vaccine available too late to contain the pandemic re-emergence. What would be really a heroic move by the US DHHS would be to go ahead an allow production of vaccine by several of the new methods using cell culture and other innovative techniques currently under development. These early stage methods have the potential to produce vaccine in less than half the time compared with using fertilized chicken eggs and can be scaled up to produce exponentially larger quantities of vaccine. Given the current state of pandemic risk, I sincerely hope they support this approach.

    If #2 occurs, then most will be caught flat footed since it will become very difficult to prepare as the panicked public rapidly deplete stocks of commodities useful for pandemic survival as well as regularly needed food and medicine. Most people take for granted that there will always be an abundance of food on the grocery store shelves. Our old nemesis, Just In Time Inventory Management will result in empty store shelves causing more panic even though food is still being produced and in a full pipeline to retailers every day. Panic buying though could keep store shelves relatively empty due to public hoarding. The risk for civil disorder would rise dramatically as a result of the public’s concern about both the pandemic as well as their perception of widespread food shortages whether true or false.

    Obviously we can all pray for scenario #3 despite its relative improbability. One good result of this is it could serve as a wake up call for our leaders and public but OTOH it might also be seen as another pandemic false alarm that increases complacency even more than has been present over the past two years.

    Grattan Woodson, MD

  32. #32 Maria
    April 26, 2009

    So, Mono, you are proposing to shut down all travel to and fro those countries?

    That may be effective in containing the spread, but it will also cost jobs and income. If the *only* thing you care about is new flu cases, then your proposed policy would be the right one. As soon as you add any other welfare indicator to your criteria, then such a drastic measure starts losing its appeal.

  33. #33 Tsu Dho Nimh
    April 26, 2009

    If Mexico is only looking at “atypical, non-bacterial pneumonias” they would be getting a skewed idea of Case Fatality rates. It’s like looking as West Nile Virus only in hospitalized people, and disregarding the larger numbers who felt nothing or had a mild illness.

  34. #34 anon
    April 26, 2009

    revere, monotreme
    it all depends on the severety and predicted amount of spread.
    There is a point, where
    closing airports makes sense.
    good sign that they didn’t do it yet.

  35. #35 Monotreme
    April 26, 2009

    Maria, I understand the economic arguments, but I do think lives trump money. Further, I have argued elsewhere that an economy based on resilience would actually improve the living conditions of most people. If you’re interested, click on my name and scroll down to the bottom of the webpage that takes you to for my views on this.

    One barrier to more aggressive public health measure is the “mild virus in the US” meme. I think this is a false characterisation of what is actually happening. Read the first hand account of a student with the virus in NYC and see if you would characterise that as mild symtpoms.

    Queens School Tested For Swine Flu After Students Complain Of Symptoms

    “My chest is really tight, it feels like a 20-pound baby is sitting on my chest,” said one student. “I have shortness of breath, I can’t even walk up the steps, and as you can hear I’m stuffy and my coughing is getting really bad.”

  36. #36 CyberLizard
    April 26, 2009

    “My chest is really tight, it feels like a 20-pound baby is sitting on my chest,” said one student. “I have shortness of breath, I can’t even walk up the steps, and as you can hear I’m stuffy and my coughing is getting really bad.”

    Sounds like quite a few days for me, what with asthma and all. I’m going to get my personal bubble ready 😉

  37. #37 Hank Roberts
    April 26, 2009

    Uh, oh:


    “Between the autumn of 1918 and the spring of 1919, 548,452 people died of swine flu in the US.”

    (I know it wasn’t “swine flu” — where do they get this stuff?)

  38. #38 Buffy the Pathogen Hunter
    April 26, 2009

    There is a difference between people independently deciding to cancel plans for foreign travel, and the government announcing a total ban into and out of a country.
    As someone who works in public health, I get asked about “what to do” in the event of an influenza epidemic. I explain to them that as the government is trying to curb the epidemic at a societal level, they can also control the epidemic at an individual level. If they stay home, don’t leave the house, and don’t let others come over, they should be safe. Stockpile plenty of canned goods and some masks for going to the grocery store, get your telework situation all set up so you don’t go crazy from boredom, and be prepared to sit tight for 2 – 3 weeks.
    Personally speaking, I don’t plan on depending on the government for anything during a pandemic. I might be be working twenty hours a day, but I will be advising my family and friends to stay home and stay put.

  39. #39 Mark Gendreau
    April 26, 2009

    My 3 cents worth:
    1.Computational modeling shows us that even the most restrictive flight restrictions (99%) only delays the spread by a couple of weeks-maybe enough time to mobilize resources but it is contingent upon the cat not being out of the bag which has already happened so flight restrictions wont help at this point.
    2.Infection spread within aircraft depends upon the source strength, exposure (duration of the exposure and proximity to the source strength) and ventilation within the space. However, no federal aviation regulatory agency-in any country- seems to think that ventilation systems within aircraft should be regulated and as a consequence there are no requirements to date in regards to certification of the passenger cabin air, or the use of HEPA filters or their maintenance for that matter (what type, how long they can be used before being replaced). With that said, most airlines do use HEPA but regional jets -you know the ones you typically fly on going from Boston to Wash DC for example, do not and a 2004 GAO investigation found HEPA filters lacking in 50 % of regional jets and 15 % in large jets. Thankfully when these filters get clogged up they cause a drag in the ventilation system which results in the aircraft burning more fuel so there is somewhat of a financial incentive to make sure the HEPA is a working if you got em. I don’t like this “scouts honor” means of regulating HEPA filters its too damn important to civilization in this era of air travel and good cabin ventilation may help minimize the spread within the cabin especially with a outbreak with a short serial interval and high theta value. I attended and testified before a Congressional hearing on the topic back during the SARS outbreak and one congressman asked the federal air surgeon: “what are we waiting for[in regard to federal cabin air certification/HEPA filter requirements} a pandemic to wipe out half the population before we regulate cabin air” -His response: “We never thought it was necessary”. Since ventilation is a keystone factor in disease spread me must ensure that airlines are doing everything to optimize good ventilation within the passenger cabin.
    3. Travel Pearl: If you do need to fly remember: ventilation is best towards the front of the aircraft and goop up your hands like your in a hospital ward with alcohol-based gel (must be high alcohol content like Purell). N95 masks only please.

  40. #40 Reiko Shimizu
    April 26, 2009

    What is the mortality rate of this virus?

  41. #41 Jon Schultz
    April 26, 2009

    Hank, actually Dr. Henry Niman of Recombinomics.com has been saying for years that the 1918 pandemic virus was of swine, rather than (or predominantly more than) avian origin. That it was of avian origin was postulated in a paper by Dr. Jeffrey Taubenberger, I believe, and the press generally reports that as fact.

    I’m not saying that Dr. Niman is correct but only pointing out that there are differences of opinion on the issue.

  42. #42 revere
    April 26, 2009

    NB to readers: Commenter Mark Gendreau above is co-author of the best and one of the most recent reviews (Lancet, Mangili and Gendreau, cited in the post), so he is as well informed as anyone. Good info and good advice. Thanks, Mark.

  43. #43 Art
    April 26, 2009

    One aspect that people in favor of travel bans seem to overlook is that millions of people are in transit. Shut down air traffic and your going to have thousands or tired, sleepless, dirty, ill-fed people crowded into airports. We see this when a snow storm stops air travel. There may not be any better way of making sure all are infected.

    Closing the airports won’t help much as these people will just back up into the surrounding community. Great numbers of people flying home on their last dollar so they can be expected to pile into cheap diners and flop houses. Isolation is impossible, basic sanitation marginal.

  44. #44 Tsu Dho Nimh
    April 26, 2009

    Monotreme said, “Read the first hand account of a student with the virus in NYC and see if you would characterise that as mild symtpoms.” Feeling shitty doesn’t qualify as severe because it’s not life threatening. He wasn’t sick enough to be hospitalized on a ventilator, and he could breathe despite the 20-lb bowling ball on his chest. He was well enough to talk to reporters.

    My grandmother lived through the 1918 influenza pandemic, and she was caring for people who were too weak to lift a glass to their lips, and who were drowning in their own lung fluids. That’s severe.

    Reiko: Mortality rate is unknown. Mexico is (or was) only reporting hospitalized atypical pneumonia cases, which makes any disease look worse than it is if you can find the ones who weren’t sick enough to go to the hospital (like all the NY students – sick, but not hospitalized).

  45. #45 Jon Schultz
    April 26, 2009

    Thanks, Dr. Woodson, for your extremely interesting post which I hope other experts will comment on. Another thing that could be considered, of course, is speeding up approval for the use of the currently-being-studied antiviral peramivir.

    It also seems to me that the government should be conducting tests to see if the inexpensive antioxidant BHT has significant value as an antiflu medicine. According to some studies it affects lipid-coated viruses, of which influenza is one. Pharmaceutical companies have no incentive to study BHT because it can’t be patented. More at:


  46. #46 Phillip Huggan
    April 26, 2009

    I think, but I’m not sure, those models assumed a relatively contagious pathogen (in rural SE Asia). In my mind if this swine flu isn’t too contagious, it will eventually burn out now that it is public. If it is too contagious it is already or will shortly be in every major airport city. In my mind there is a window where measures like reducing non-essential air travel to/from Mexico can slow the spread from two dozen presently cat-out-of-the-bag cities, and the remaining 200 cities that aren’t at least reporting potential cases. Just my opinion. But if the death toll is low enough, no need to Great Depression world economy. Just my opinion, but for a 1-2 day incubation period it should’ve spread like wildfire if highly communicable. If I’m wrong, why r u listening to a high school dropout?!

  47. #47 Monotreme
    April 26, 2009

    Dr. Gendreau, I appreciate you commenting on this point. However, I have to say that when I have to choose between empirical data and computational modeling, I always go with the former. All of the empirical data, and common sense, suggest stopping the vectors of flu, humans, from moving from point A to point B will stop the spread of the virus. I really don’t think this is in dispute. What is in dispute is whether it is possible to implement strict travel restrictions. With all due respect, I would suggest that epidemiologists are not the content experts on this topic. Computer models can be fed all sorts of imaginary data and/or use any number of assumptions. As I’m sure you know, garbage in, garbage out applies. Has anyone ever modeled the effect of closing airports down, period? If you are aware of study on that intervention, please point me to it.


  48. #48 Tom DVM
    April 26, 2009

    I completely agree with Monotreme.

    Here’s where I draw the line.

    If the symptoms and CFR were exactly the same between Mexico and the United States and Canada etc…then it would seem that a travel ban at this point would be of limited usefulness.

    However, this is not the case. The bug itself has seemed to draw a line for itself on the Mexican border…

    …on one side of the border it has an apparent CFR that would put it in the class of more virulent pandemics like 1918….and on the other side is a flu with ‘mild’ symptoms.

    Under these specific conditions, it would seem that I could and would ethically institute not only an air travel ban but also a land travel band for a few days or a week until I sorted out the potentials.

    Of course the World Health Organization has squandered the chance to isolate the more virulent strain-subtype in the hopes of eradication, if there is one…and at this point they don’t know one way or another…they are guessing.

    So we have tourists continuing to visit Mexico as we speak, ensuring that the world will be seeded unnecessarily.

    It seems likely that the virus will go into hiding (dormant) shortly to come back with a vengance at some point in the future…a October-November 2009 or a few years.

    When it does so, we will have the World Health Organization to thank…

    …and if the more virulent form escapes now to seed the rest of the world…we will wish that we instituted Monotreme’s travel ban as many will die waiting for the vaccine.

  49. #49 Buffy the Pathogen Hunter
    April 26, 2009

    “What is in dispute is whether it is possible to implement strict travel restrictions.”

    Not until it’s too late. The political will to inflict the kind of economic damage associated with a total travel ban will not materialize until huge numbers of people have already died.

    Part of the difficulty of public health is that success means nothing happens. If the government by some miracle ever did put a travel ban into place very early on in an epidemic, it would stop the epidemic, and the media etc. would be like, “You totally overreacted! We lost $20 billion due to the travel ban, and only three people died.”

    And then the next time an outbreak occurs, the politicians won’t want to shut down travel because of the backlash.

    Officials should be encouraging people everywhere to delay all non-essential travel to and through Mexico. As a non-coercive order it can be issued relatively easily, and it could help people understand that right now, they really shouldn’t be going to Mexico.

  50. #50 K
    April 26, 2009

    Revere is right. Note below the history of the 1918 flu when air travel was sparse – heck it spread to remote Pacific Islands and the Artic. Border closings are a waste of time. As soon as 1 person leaves the country with it, it is wherever they took it. At any rate since it is now in the US the practice of closing borders would mean that ALL countries that do not have it should close their borders to anyone from the US.

    per wiki
    “The 1918 flu pandemic (commonly referred to as the Spanish flu) was an influenza pandemic that spread to nearly every part of the world. It was caused by an unusually virulent and deadly Influenza A virus strain of subtype H1N1. Historical and epidemiologic data are inadequate to identify the geographic origin of the virus.[1] Most of its victims were healthy young adults, in contrast to most influenza outbreaks which predominantly affect juvenile, elderly, or otherwise weakened patients. The pandemic lasted from March 1918 to June 1920,[2] spreading even to the Arctic and remote Pacific islands.”

  51. #51 James Bowery
    April 26, 2009

    Mark Gendreau writes: “1.Computational modeling shows us that even the most restrictive flight restrictions (99%) only delays the spread by a couple of weeks”

    Where may I download the program?

  52. #52 Tom DVM
    April 26, 2009

    ‘Officials should be encouraging people everywhere to delay all non-essential travel.’

    Well Buffy, the World Health Organization doesn’t have either the strength or commitment to even do that!

  53. #53 Buffy the Pathogen Hunter
    April 26, 2009

    ‘Officials should be encouraging people everywhere to delay all non-essential travel.’
    Well Buffy, the World Health Organization doesn’t have either the strength or commitment to even do that!”


    Apparently, neither does the CDC:

    “And while there are no travel restrictions issued for Mexico, CDC spokesman Tom Skinner advises people who plan on traveling to Mexico, “to take the measures they can take to protect themselves, like frequent hand-washing.”

    Ooooh, hand-washing. I feel so safe.

  54. #54 Tom dVM
    April 26, 2009


    In part, that has been my point.

    The World Health Organization leads…and everyone else follows.

    The World Health Organization is the excuse used by Governments and regulators for inaction.

    …and while I’m at it…are they subject to independent oversight…and also do they disclose potential conflicts of interest including trading in shares of pharmaceutical companies etc…

    …and also, are they permitted to be hired by the very pharmaceutical companies that stould to benefit from their decisions immediately after they leave the WHO.

    It is cloaked and shady just like it’s parent…subject to ‘graft’ just like its parent.

    This has and will have an effect on our lives in the near future because right behind this is the main event…H5N1!

  55. #55 PB
    April 26, 2009

    First off, it is too early to know whether the CFR is is lower in the US, both because of the small number of people infected here, and because we have no reliable estimate of how many people are infected in Mexico. Even the number of deaths in Mexico will require some time to sort out.

    That said, one possible reason for high mortality in Mexico is a synergistic effect with TB, which has a higher prevalence there. Andrew Noymer’s work on the 1918 pandemic suggests that the spanish flu basically killed off everyone carrying TB, and you can see it in the sharp decline in TB deaths in the period immediately after 1918. The current flu has a similar age structure to its mortality. Time will tell whether that’s part of the story this time around. In the meantime, we might want to consider some serious outreach for testing and treatment of TB in Mexican immigrant communities here.

  56. #56 cojemema
    April 26, 2009

    Would that be a concern for people with active TB only, or dormant TB as well?

  57. #57 PB
    April 26, 2009


    from what I recall of Noymer’s article, the initial finding was based on the reduced TB mortality immediately after the 1918 pandemic. In other words, it killed the people who would have died from TB over the next few years all at once. So those would have been active cases. However, that data doesn’t really answer the question as to whether having dormant TB might also put one at a higher mortality risk. I suppose that would depend largely on whether infection with this flu would cause dormant TB to reactivate.

  58. #58 Lavendr
    April 26, 2009

    Re. NZ cases. One of the teachers from the school group just back from Mexico has been hospitalised now. The variant still hasn’t been identified although health officials believe it’s likely to be swine flu. One other member of the party had been hospitalised but is now home after receiving anti-virals.


  59. #59 M. Randolph Kruger
    April 26, 2009

    Mono-the guys who did that model like 3 years ago took that into account when they came up with that generated graphic for spread. In fact it was supposedly tilted towards the airport as prime vector and general transportation second. They have already tossed the towel in on that I think as it frees up resources that might otherwise be used as a containment instead.

    Its still a state run operation for the time being. Obama’s declaration of a state of emergency still will not allow introduction of any troops or really any federal authorities on their turf until they sign the federalization orders. That was changed after Katrina, then the Dem Congress changed it back again. So the next Blanco is waiting to happen with the question only being how many before they call it individually. Its jumping down Memphis way for freight ops on a Sunday…Masks are being seen on the main concourse.

    Here are a couple of dozen models. Pick one and draw what you think may be right. It works as you say via variables. I can program a computer to say that bird flu is the cause of global warming. Nuances in the programs beyond general spread I think are worthless after the first couple of cities go down.

    I am like you. I can deal with what I can see and not a computer that can run the game on me.


  60. #60 swine flu symptoms
    April 26, 2009

    Be interesting to see what if any impact this swine flu issue has on the desire of some to increase urban density afterall some will argue that increased density will help diseases spread.

  61. #61 Otto
    April 27, 2009

    While there aren’t any pig farms in Israel

    Sure there are.

  62. #62 revere
    April 27, 2009

    Otto: Thanks. Didn’t know that.

  63. #63 Stoker
    April 27, 2009

    BBC reports two cases in Scotland confirmed : http://news.bbc.co.uk/

  64. #64 Michael A. Bailey
    April 27, 2009

    As I teach pathogen courses in the workplace:
    Is this an airborne pathogen?
    What precautions could/should a person take?
    Is resperatory protection suggested? Helpful?

    As I do a pathogen course, any PPE suggested?

    Michael A. Bailey
    Casper Wyoming

  65. #65 Ethan Romero
    April 28, 2009

    Some people were asking for citations to papers on simulations of the efficacy of travel restrictions. The following paper (free text or pdf) looks at multiple interventions including travel restriction.


  66. #66 Mikeo
    April 28, 2009

    Closing down the airports seems like a logical course of action. Stop the spread and deal with the illness? I am amazed governments are still ‘advising against’ travel to Mexico, worrying indeed.

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