Tag Archives: How diseases spread

Zombietown USA

7 Apr

I’ve written several posts about zombies and science, and I probably shouldn’t be writing another one now, but I came across something which I couldn’t resist writing about, and this is Zombietown USA. Zombietown USA is a simulation of a zombie outbreak in the contiguous states of the USA which uses a standard epidemiological model to examine how it would spread.

There have been plenty of these types of models before, even on the spread of zombie diseases, but this one is different. Why? Because it lets you change the parameters and explore exactly what effect this has on how the disease spreads. This means you can not only create your own personal zombie apocalypse, but you can also work out exactly where the best place to hide would be, in the event of one ever happening in a town near you.

So what are the parameters you can play around with? Well, they’re quite simple. They are the starting location, the kill-to-bite ratio and the time it takes a zombie to walk one mile. The start location and the speed that zombies can move are both self-explanatory (although it’s nice to see that they have modelled both traditional slow zombies, and the more recent fast zombies), but the kill-to-bite (KTB) ratio needs some explanation. The KTB ratio is the relative effectiveness of zombie biting humans to humans killing zombies. According to this article from Computing World, they initially used a KTB ratio of 0.8 (meaning that for every zombie killed, 1.25 humans were bitten and infected), which they derived from watching zombie films such as Night of the Living Dead and Shaun of the Dead.

Once, you’ve set these parameters to whatever values you want to use, and chosen your starting location, you can then set the modelling running and see what happens. Perhaps unsurprisingly, when they did this for themselves using various different scenarios, the physicists behind the model found that it would take about four weeks (or 28 days – a familiar number to zombie fans!) for most of the continental US to become overrun. Interestingly, however, it would then take a lot longer for the remaining few pockets of humanity to fall, and these would be in sparsely populated areas like Montana and Nevada. They also found that if you live in a densely populated area, like northern Pennsylvania, they you are pretty much screwed!

These, however, are just general patterns. If you live in the continental US, and you want to find out what would happen if there was a zombie outbreak in your town, and where you could best go to survive it, then you can go to the Zombietown USA website, set the parameters to your own chosen values and start the model running (although, you should note that your browser will need to be able to run JavaScript for it to work, and I needed to use Google Chrome rather than Internet Explorer for this reason, in order to get it to work). I promise you that watching as the outbreak you’ve just started creeps slowly across the map will be hypnotically addictive (although make sure you set the step rate high enough so that you can see what’s happening), and you could easily waste a whole day playing with different scenarios, but then again, is there anything wrong with that? So, if you’re a zombie fan, then I would urge you, forget work for a while and go check it out*.

*Note: Follow this advice at your own risk, and the author bears no responsibility for loss of income, angry bosses, unfinished reports, missed presentations, getting fired, or any other unpleasant side-effects of doing so!



*****************************************************************************
From the author of For Those In Peril On The Sea, a tale of post-apocalyptic survival in a world where zombie-like infected rule the land and all the last few human survivors can do is stay on their boats and try to survive. Now available in print and as a Kindle ebook. Click here or visit www.forthoseinperil.net to find out more. To download a preview of the first three chapters, click here.

To read the Foreword Clarion Review of For Those In Peril On The Sea (where it scored five stars out of five) click here.

How Outbreaks Spread … Or Why I’m Moving To St. Helena Just In Case There’s A Zombie Apocalypse

16 Dec

For there to be a zombie apocalypse, the disease which turns people into zombies must spread. Traditionally, it’s always been assumed that diseases spread geographically, and that the closer you are to the source of an epidemic (whether zombie-related or not), the sooner you are likely to encounter it. For most of human history this was, indeed, the case. However, in the last fifty years or so this has gradually changed, and now things are quite different. This is because, thanks to the ubiquity of modern air travel, the way the world is connected has changed. This has led to a disconnect between the geographic distance between any two points on the planet and the transmission distance (which measures the ease by which a disease can get from point A to point B).

This means it is now easier for a disease to spread from London to New York, despite the several thousand miles of water between them, than between London and Cape Wrath at the far northwestern tip of Scotland, which is only a few hundred miles away on the same island, but which has no direct connections of any kind to London (the two are not even connected by road). Indeed, a disease might find it easier to get from London to Sydney, Australia, on the other side of the world, than from London to Cape Wrath because of the way airlines now connect the world.

While this might be intuitively obvious once someone points it out, it’s only recently that this has started to be incorporated into our understanding of how diseases spread. Of particular interest here is the work of theoretical physicist Dirk Brockmann, who, along with a number of colleagues, has created a mathematical model of how the connectivity resulting from modern air travel affects how diseases, such as SARS, swine flu or (in theory at any rate) a zombie virus, spread around the world, but you don’t have to understand maths to be able to see what’s going on. This is because he’s used his model to produce some really beautiful and interesting videos, like the one below, to show what’s going on.

The video below starts with an outbreak of a disease in Atlanta, Georgia, and shows how it rapidly spreads around the world along the air routes which radiate out from this air hub.

For those of us interested in creating zombie apocalypse stories, these new models of how diseases spread in the modern world can help us create more realistic scenarios for how a zombie epidemic caused by a disease might be transmitted around the world. For those who worry that it’s only a matter of time before a zombie apocalypse actually happens, it can also be very informative as it highlights where in the world you’d have your best chance of avoiding being caught up in the outbreak.

For this reason, I’ve been looking around for possible places to relocate to just in case there’s a zombie apocalypse looming over the horizon, and based on the connectivity suggested by the above model, I think I have the perfect place: the small tropical island of St. Helena in the South Atlantic. It has no airport and is two days by sea from the nearest airstrip (on Ascension Island, which, in itself, is hardly a major air hub!). I think I’d be pretty safe there. As it happens, I’ve also been there as part of my day job as a marine biologist, and I can tell you from experience, it’s a really nice place and I could think of a lot worse places to hole up while waiting for the world to come to an end.

***

If you want to find out more about Dirk Brockmann’s research on how diseases spread, click here.



*****************************************************************************
From the author of For Those In Peril On The Sea, a tale of post-apocalyptic survival in a world where zombie-like infected rule the land and all the last few human survivors can do is stay on their boats and try to survive. Now available in print and as a Kindle ebook. Click here or visit www.forthoseinperil.net to find out more. To download a preview of the first three chapters, click here.

To read the Foreword Clarion Review of For Those In Peril On The Sea (where it scored five stars out of five) click here.