Bird Flu

[uuDevil]

I just read this article on Yahoo (http://story.news.yahoo.com/news?tmpl=story&cid=514&e=15&u=/ap/20050223/ap_on_he_me/bird_flu_20) and was mildly surprised by this quote:

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We at WHO believe that the world is now in the gravest possible danger of a pandemic," Dr. Shigeru Omi, the WHO's Western Pacific regional director, said Wednesday.
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He said the world is "now overdue" for an influenza pandemic, since mass epidemics have occurred every 20-30 years. It has been nearly 40 years since the last one.

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Is this a sound argument?

[gaming_mouse]

This is not a pure math question. Whether or not a long spell without an epidemic makes one more likely needs to be answered empirically. It's not clear what forces are at work here.

[NiceCatch]

I'll have a flu-shot please. Bird flavor, thanks.

[uuDevil]

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This is not a pure math question.

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Good point.

Thing is, we could say that about any application of math to an actual physical phenomenon. Questions involving the distribution of cards dealt or coins flipped aren't really pure math questions either, but I wouldn't argue that "I'm due for pocket aces." At least not around here. /images/graemlins/wink.gif

It appears to me that Dr. Omi is appealing to probability to argue that we are more likely to see this pandemic occur now than we were in the past. So whatever the underlying reality, I don't think his argument holds water. Or am I missing something?

[uuDevil]

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I'll have a flu-shot please. Bird flavor, thanks.

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I'm just getting over the flu. Ugh. I'll take one too.

[NiceCatch]

Aren't we also like several thousand years overdue for a global ice-age? That, coupled with the bird-flu, could really ruin my day.

[uuDevil]

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Aren't we also like several thousand years overdue for a global ice-age? That, coupled with the bird-flu, could really ruin my day.

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We immunized ourselves against the ice-age by pumping CO2 into the atmosphere. I fear we may have overdone it, though. /images/graemlins/frown.gif

[MickeyHoldem]

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We immunized ourselves against the ice-age by pumping CO2 into the atmosphere. I fear we may have overdone it, though.

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Speak for yourself.... Currently -24 C as I type this...brrrrr!

Note: this is a humour posting, not an attempt to debate global warming! All replies will be politely ignored!

[lu_hawk]

it is valid to say that each year's flu is not an independent outcome. there is a sequence of events that will lead up to the next pandemic. however, i really don't know how much this actually effects the outcome. so if we go 50 years without a pandemic the odds of one happening would be higher than if we just had one 2 years ago but i don't know if there is any way to say if it is 2% higher or 50% higher.

[gaming_mouse]

[ QUOTE ]
Thing is, we could say that about any application of math to an actual physical phenomenon. Questions involving the distribution of cards dealt or coins flipped aren't really pure math questions either, but I wouldn't argue that "I'm due for pocket aces." At least not around here.

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It's not really analogous. Coin and card questions really are pure math, or at least they are so close to it that the assumption is okay to make. Of course, you could argue that which side a coin lands on is not really random -- since its determined by the laws of physics -- but its behaviour is almost perfectly described by the assumption of randomness. Saying you are "due for a head" is incorrect. It is not clear that saying we are "due for a flu epidemic" is incorrect, although it might be. That is, we have mounds of evidence that coin flips are independent of one another. There is no such evidence -- at least not that I know of -- that flu epidemics are.

gm

[uuDevil]

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That is, we have mounds of evidence that coin flips are independent of one another. There is no such evidence -- at least not that I know of -- that flu epidemics are.


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Independent or not, there is likely some probability model that approximately fits the behavior of flu epidemics. In any case, the good Dr. is assuming that there is, and I am willing to grant him that.

To put the question a different way, if someone who understands probability, say BruceZ, were to make the statement: "Given probability model X, we are overdue for event Y," what attitude toward this statement is most justified?

a) "BruceZ is right, of course."
b) "BruceZ is speaking loosely, he really means alternate statement Z."
c) "BruceZ has lost his mathematical marbles."

Also, if b), what might statement Z be?

[With apologies to Bruce /images/graemlins/wink.gif]

[uuDevil]

[ QUOTE ]
it is valid to say that each year's flu is not an independent outcome. there is a sequence of events that will lead up to the next pandemic. however, i really don't know how much this actually effects the outcome. so if we go 50 years without a pandemic the odds of one happening would be higher than if we just had one 2 years ago but i don't know if there is any way to say if it is 2% higher or 50% higher.

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If the underlying distribution is somehow such that the probability is increasing with time would that be enough to justify saying "we are overdue"? Or is there some other circumstance that would justify it?

Basically I just want to know what my attitude toward a government official who makes this statement should be.

[jnglegeo]

Interesting thought.....We have had an assasination or attempted assasination of every president voted in at the beginning of every even numbered decade going back to lincoln...(Reagan-1980 Kennedy-1960..etc..) Does that mean we are overdue for one now too?

[gaming_mouse]

[ QUOTE ]
To put the question a different way, if someone who understands probability, say BruceZ, were to make the statement: "Given probability model X, we are overdue for event Y," what attitude toward this statement is most justified?

a) "BruceZ is right, of course."
b) "BruceZ is speaking loosely, he really means alternate statement Z."
c) "BruceZ has lost his mathematical marbles."


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I'm not sure I understand what you are asking. Certainly, there do exist models where the concept of overdue makes perfect sense. In these models, events are not independent -- so that a dry spell will indeed make an event more likely.

Wheather or not one of these models fits with a flu epidemic is, again, a matter to be empiracally determined.

[uuDevil]

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Certainly, there do exist models where the concept of overdue makes perfect sense.

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If that's the case, I have to cut Dr. Omi a little slack. Thanks.