How likely is an avian flu pandemic?

Poisson distribution

With winter approaching, many governments in the northern hemisphere are stocking up on Tamiflu and fine tuning their civil defense plans to cope with the disruption a bird flu outbreak might cause.

But how likely is an outbreak? While various groups have written about how a pandemic might happen, Rinaldo Schinazi at the University of Colorado says nobody seems to have bothered to work out the probability of such an event.

That sounds unforgivable, given the investment that’s going in to tackling the problem. But in some ways it’s understandable. Schinazi says:

“The occurrence of a pandemic seems to be hopelessly complex in the sense that it depends on a multitude of factors, some known others unknown. Factors mentioned in the literature go from the stability of the current influenza strains to the number of pigs in China! Hence, a model taking into account all known factors would probably be as complex as the phenomenon itself, would not be that accurate and would therefore be useless.

But Schinazi has taken an entirely different approach:

“We do not attempt to incorporate into the model any of the factors that are believed to provoke a pandemic. Instead we treat the occurence of a pandemic as a purely random phenomenon.

And the result is a fascinating read. It turns out there have been only 10 pandemics in the last 300 years. This is the data Schinazi uses to prime his models.

Assuming a Poisson distribution, the mean time between pandemics is 30 years but the probability that no pandemic occurs in 60 years is 14% .

Assume a random walk model and the probability that the time between two pandemics is at least 50 years becomes 11% but the probability that this interval is at least 100 years is 8%, which is hardly much less.

Schinazi’s conclusion is both surprising and re-assuring: the next pandemic might not be as imminent we’ve been led to believe.

Ref: Will the Announced Influenza Pandemic Really Happen?

3 Responses to “How likely is an avian flu pandemic?”

  1. aurora says:

    Assuming his math is correct, would you get on a plane if you knew there was a 14% or 11% chance of it crashing into a mountain?

  2. Kent says:

    Terrible terrible assumptions. Planes,trains,cars, hell even bicycles were invented in the last 300 years. This allowed mass movement of people spreading Pandemics more quickly. The develop of immunization medication & anti-biotics would have prevented many pandemics from occurring which would have otherwise occurred 50 years ago. Also due to the uncareful distribution of anti-biotics, any viruses that develop are likely to be more resilient that 20 years ago.

    Although I agree that a statistical approach has to be taken. Valid assumptions have to be made.

    A side question on this whole matter is, how much money does Donald Rumsfield, who has a large number of shares in the pharmaceutical who produced Tamiflu, stand to gain if the risk of a pandemic is overly hyped?

    Nothing is as it seems in this universe of ours…

  3. akinin says:

    ghastly assumptions
    what about population growth and increased travel?
    it’s comparing apples to intergalactic oranges.