If zombies actually existed, an attack by them would lead to the collapse of civilisation unless dealt with quickly and aggressively.

That is the conclusion of a mathematical exercise carried out by researchers in Canada.

They say only frequent counter-attacks with increasing force would eradicate the fictional creatures.

"The scientific paper is published in a book - Infectious Diseases Modelling Research Progress. "

My understanding of zombie biology is that if you manage to decapitate a zombie then it's dead forever

According to the researchers, the key difference between the zombies and the spread of real infections is that "zombies can come back to life".

Professor Neil Ferguson, who is one of the UK government's chief advisers on controlling the spread of swine flu, said the study did have parallels with some infectious diseases.

"None of them actually cause large-scale death or disease, but certainly there are some fungal infections which are difficult to eradicate," said Professor Ferguson, from Imperial College London.

The latter problem may be less intuitive so I'll explain my reasoning: Humans who survive the initial outbreak survive for a reason. Disproportionately, they were faster, smarter, and stronger to begin with than their fallen peers. Even if they weren't, they were luckier and have probably been able to, at least, find a more defensible location than where they started at round zero of the outbreak, increasing their chances of survival simply by virtue of having survived the early rounds of the outbreak.

So, I constructed a computational agent-based zombie outbreak model to test how my assumptions might alter the solution.

[T]he [Carelton University] team's model leaves something more profound out the equation: human capacity for ex-post organization and response. When accounting for these things, I can find scenarios of large initial zombie outbreaks that, when followed by quick adoption of strong anti-zombie defense policies may help pockets, or even large fractions of civilization to ward off the impending doom of mass zombie infection! How exciting!

If] the Romero movies have taught us anything, it’s that the defensive resources are only effective if they aren’t sabotaged by the internal squabbles of humans. (If you’re not familiar with Romero’s movies, think of what Newman from Seinfeld did in “Jurassic Park”). Thus you’d have to add another parameter, which is the probability in any given period that some jackass sabotages the defensive perimeter, steals the battle bus, etc. If such sabotage eliminates or even appreciably reduces the “safe area” efficacy then human survival in the “safe areas” is contingent on the act of sabotage not occurring....

So a more elaborated model would not only have to add in parameters for spatial heterogeneity, but also human sabotage.

[T]he prospect of a zombie apocalypse actually represents a chance to throw off the constrictive fetters of society, shoot your neighbours in the face, steal some guns and a car, and drive off into the sunrise, taking along only those friends and family you trust and care about the most. As such, it represents a simplifying of life.