Posts tagged with zombies.

Science tackles zombie attacks

Jennifer Gardy, August 10, 2009 at 11:07 AM

My apologies for the prolonged radio silence - it turns out the real world is a rather busy place. I have a sneaking suspicion that this may have something to do with the fact that I am working at a Centre for Disease Control IN THE MIDDLE OF A PANDEMIC, but I haven't got a control job in place so cannot reliably confirm whether my hypothesis holds true with any measure of statistical confidence.

I can, however, confirm that working in the realm of infectious disease research is tremendously interesting. Global surveillance is constantly turning up cases of the usual assortment of gnarly human ailments, from anthrax to rabies to pneumonic plague, and the animal kingdom is verily rife with exotic zoonoses. In the last two weeks, for example, I have received reports on Ecuadorian penguins with malaria, herpetic horses, a tuberculotic cow, and a bunch of vampire bats with SARS.

All the rabid humans, coughing cows and sneezing febrile bats of the world, however, cannot even come close to the most interesting bit of infectious disease research I've come across lately - the mathematical modelling of the potential outcomes for humanity should zombies attack.

I came across the paper a couple of weeks ago, when I was giving a workshop on practical conference-going skills to a group of students about to attend the Annual Meeting of the Society for Mathematical Biology. The pre-conference meeting also featured introductory lectures from many of the conference session chairs, 45-minute cheat sheets introducing the students to the different areas the conference plenary sessions would cover. I arrived early to the check out the session before mine - an introduction to mathematical modelling of infectious disease - and discovered Robert Smith?'s (yes, that is a question mark) zombie model.

Now I am certain that most readers will agree with me when I say that mathematical modelling does not sound like the most compelling of subjects. Partial differential equations, eigen decomposition and matrix diagonalization are all very important concepts that the advanced undergraduate in physics, engineering, or math ought to be familiar with, but when one is being taught the aforementioned concepts through examples that include latent semantic analysis and pharmacokinetic cumulation processes, the material can get a little, uh, dry.

When you use zombies as your example process, however, students sit up and take notice.

There is no nerd on the face of this earth who hasn't at least idly considered what they'd do in the event of a zombie attack, and there are a good many more of us who have actually thought through our specific plans and debated their various benefits and pitfalls with others (my solar-powered-chainsaw-studded fence, for example, while brutally effective in the short term, would likely soon enough result in the build-up of a ramp of zombie carcasses in front of the fence, blocking the chainsaw blades. See, it's good to think of these things now.)

Smith? and his colleagues decided to apply the basic principles of mathematical modelling to a zombie outbreak situation. They define a series of classes to which people can belong (susceptible, zombie, or removed) and a set of parameters modelling the transition between classes (the rate at which susceptible become zombies, for example). From this they can construct a basic epidemiological model that predicts how quickly zombies will take over the world. The model can be successively refined by adding new parameters, like the effect of quarantine, treatment, or what the authors politely refer to as "impulsive eradication" (nuking the $#!% of the zombies, in other words).

By explaining a highly technical scientific method using a flat-out cool pop-culture example, the authors manage to make concepts like Jacobians, unstable equilibria, and mass-action transmissions infinitely more palatable and memorable to students and researchers alike.  The approach is one more and more profs are adopting - at UBC, for example, a second-year physics course in instrument design is taught as a Robot Wars-eqsue competition, where the students build robots to carry out a specified task and then battle it out of at the end of term to see whose robot emerges triumphant. In my own work, a colleague and I recently jazzed up a textbook chapter on the computational analysis of immunology data by using an exotic and disgusting case of purulent smallpox as our example dataset.

Using a catchy example is a fantastic way to engage students with your subject matter. For proof, you need to look no further than the fact that you, dear reader, kept reading past matrix diagonalizations and mass-action transmissions to find out what happens to humanity in the event of a zombie outbreak. The bad news is that in most cases - the basic model, the latent infection model, the small-scale quarantine model - the disease-free equilibria are unstable and zombies take over the world. Treatment doesn't do a fat lot of good either, as humanity continues to exist but at much lower population numbers than before the outbreak. The good news, however, is that under the model of impulsive eradication, in which large-scale assaults on the zombie population take place as resources permit, humanity survives. So stock up on nukes, folks - the ordinary differential equations don't lie.

Tagged with mathematical, teaching, zombies, modelling | Comments (31) |