Tag Archives: rabies

What Are The Chances Of There Being A Zombie Apocalypse In Your Lifetime?

31 Jul

We all know that there are zombie apocalypse preppers out there, and many think that they’re simply wasting their time because a zombie apocalypse could never happen. However, what if they are right and it is the rest of us that are wrong? Isn’t it better to be prepared and have nothing happen, than not be prepared and get caught out?

Well, that all depends on the risk of it happening. As with anything in life, we need to know how likely (or unlikely) something is to happen before we can decide whether we should take precautions and how much time and money we should put into them. Yet, how is this risk calculated? How on earth would you calculate the risk of being killed in a zombie apocalypse?

Let’s take a look at how risk is calculated by looking at mortality risk. This is effectively the chance of something killing a person multiplied by the number of times it can potentially happen over a given length of time. This is worked out by taking the number of people that die from a specific cause, dividing it by the total number of people exposed to give the chance of each individual dying because of it. This figure is then divided by a measure of time to get the death rate. This death rate can then be expressed in a number of ways, but the most common is the micromort. What is a micromort? It’s a one in a million chance of dying from a specific cause (which is about the same chance of throwing 20 coins into the air and them all landing heads up). So that’s the theory, but how does it work in practice?

Well, if we wanted to work out the risk of being murdered in the UK (where I live), we can work this out as follows: There were 640 murders in the UK in 2011. This is out of a population around 61.37 million. So we divide 640 by 61.37 million and find that each individual has a 0.00104% chance of being murdered each year. To work out this value in micromorts, we then multiply it by a million and find that the risk dying from an external cause in the UK each year is 10.4 micromorts.

But is 10.4 micromorts a lot or a little? To find that out, we need to compare that to other causes of death. The chances of dying because you spend one night in hospital in England is 75 micromorts. So, each year, you’re 7.5 times more likely to die from having to spend a night in hospital in England than of being murdered. Similarly, you’ve got about the same chance of dying each time you’re were given a general anesthetic as being murdered (10 vs 10.4 micromorts) and you’re eight times more likely to die each time you give birth in Britain than being murdered in any one year (and you’re 17 times more likely to die while giving birth in the US than of being murdered in any one year in the UK). Of course, that’s just the UK. In The US, the risk of being murdered is almost five times higher than in the UK at 48 micromorts, while in Canada it’s 16 micromorts.

So, that’s how risk calculations and micromorts work, but how do we apply this to work out the chances of a zombie apocalypse happening and, indeed, the chances of you dying in a zombie apocalypse? First, we need to set the parameters for our zombie apocalypse. When we do this, we need to be realistic about this and follow the rules of how the world actually works. This means it can’t be dead people coming back to life, that’s just biologically impossible. However, we can have diseases which take over people’s brains and make them act like flesh-eating zombies from the movies that will attack any other human they get hold of. There’s a surprisingly large number of real diseases that can do that, but I’m going to focus on one real ‘zombie’ disease and that’s rabies.

Rabies really does take over people’s brains and make them act violently to others, and it’s transmitted by bites, but there’s two things which stop it creating a zombie apocalypse. The first is that it’s 100% fatal so anyone infected with it dies (at least if they’re not treated before they start showing symptoms). The second is that it’s not easily transmitted from one person to another. In fact, there are no known cases of human-to-human transmission. This isn’t because the disease isn’t infectious, but rather because human teeth are actually remarkably poor at being able to bite through human skin. Also, for obvious reasons, we tend to keep well clear of people who are staggering around, foaming at the mouth and trying to bite us. Together, these make it hard for humans to transmit the disease to each other.

But what if this were to change? Diseases mutate all the time and it is not inconceivable that the rabies virus could mutate in such a way that would make it less fatal, and easier to transmit. Indeed, there is already evidence that some strains of rabies are already evolving towards being able to spread much faster and more efficiently between animals without the need for bites.

So what’s the risk of this happening? If we assume that the natural mutation rate of the rabies virus is 0.00001, that is for every 10,000 times it copies itself, there’s one mutation which changes something about how it operates. Some of these mutations may be good for the virus and some may be bad, but we’re looking for very specific mutations that would change the virus in a very specific way. Thus, out of all the mutations, maybe only one in a billion might have the effect we’re interested in. Taken together, that means that there’d be a 1 in a ten trillion chance of just the right mutation happening. You’d think that would make it so unlikely that we’d never need to worry about it, but you’d be wrong. Why? Because of the law of very large numbers.

The law of very large numbers means that even very unlikely outcomes can happen if we do something often enough. You see, there isn’t just one rabies viral particle in anyone who’s infected, but millions of them, all reproducing, all the time and so all at risk of mutating in just the right way. If we take the figure of 1 million as a highly conservative estimate of the number of viral particles in any one person with rabies, and say that each one reproduces once every 10 days (again highly conservative), then within any infected individual there’s a 0.0001% chance of the required mutations occurring. Still a very small chance, but much more likely than 1 in a 10 trillion, and that’s just in each 10 day reproductive cycle in each person.

A typical person may survive for 12 weeks after infection, so there would be around eight such reproductive cycles in each person. This brings the risk of the required mutation happening in any one infected person up to 0.0008%, and around 50,000 people are infected each year, which means that when all the viruses across all the people are considered, there’s a 42% chance of the mutations happening in any one year. Just because we’re dealing with very large numbers, we’ve suddenly gone from a risk that’s infinitesimally small to one that’s almost the same as guessing whether a coin will land heads up or tails.

Rather shockingly, that means there should be a rabies-related zombie apocalypse once every 2.4 years. If we assume that 80% of the world’s population of seven billion would be killed or infected if a zombie apocalypse were to happen, then this would equate to 2.3 billion micromorts each and every year. Now, compared to out 10.4 micromorts for being murdered in the UK, that’s pretty damn high. It means that in any one year, you’d be almost 50 million times more likely to be killed in a zombie apocalypse than of being murdered, which is pretty wild and suggests that most people are worrying about all the wrong things when it comes to what’s likely to kill them.

Now, at this point, you might be thinking to yourself that you don’t remember any zombie apocalypses happening recently, and even though you’ve been pretty busy for the last 2.4 years, you’re pretty sure you’d remember 80% of the world’s population getting wiped out. So, if these are the odds, why hasn’t it happened?

Well, this is most likely to do with two things. The mutations which might make rabies more transmissible between humans might also make the virus itself less fit, and that means any viruses which carry the mutations are pushed out by those which don’t so they cannot get enough of a toehold to become the dominant type of virus in any one individual. This in itself would be enough to stop any copies of the virus which carry the required mutations from breaking free and rampaging across the planet. In other words, the virus itself might be keeping dangerous mutations in check simply because they have to compete with other versions without the same mutations for the limited resource which is the human body.

Secondly, it might be that the rabies virus simply cannot generate the mutations needed to turn it into a supervirus capable of taking over the planet. A mutation can only change what a viral gene already does. It cannot suddenly create a brand new gene that does something completely different (like genetic engineering can do). It’s just like a car, you can fiddle with the engine to make it go faster, but you can’t, just by tweaking it here and there, suddenly turn it into an aeroplane. There just aren’t the existing building block there to do that. So it might be with the rabies virus, that no amount of tweaking could ever turn it into a civilisation-destroying, zombie-apocalypse-creating megavirus that would wipe humanity from the face of the planet, but we don’t know for sure. Maybe it’s not a one in 10 trillion chance mutation, but one in a ten thousand trillion. Very unlikely, but still possible given enough time (in this case about 238,000 years – short by our lifespans, but not long in terms of how long humans have been roaming the planet, picking up rabies from other species – and that still gives it a value of 2384 micromorts per year, still high in comparison to the risk of being murdered).

So what can we learn from all this? Well, firstly, if you do anything often enough, even the most unlikely events can happen, and what has a very low probability of happening to each individual, might be quite likely to happen when there are 7 billion people on the planet – after all, someone has to guess the right numbers and win the lottery, it’s just very unlikely to be you.

Secondly, just because you can calculate the likelihood of something happening, it doesn’t necessarily mean that it will. In particular, if you don’t take everything into account properly, your calculations can go very wrong (in case of the above, assuming that the types of mutations required to turn rabies into a zombie-apocalypse creating megavirus are actually possible).

Finally, as long as you’re not talking about risen-from-the-dead type zombies, a zombie apocalypse is possible. There are diseases out there which can take over the brain and turn humans into zombie-like killers and it’s biologically feasible that they could mutate to create a highly infectious zombie-like disease. Given the numbers, even if such a mutation was very, very unlikely, there’s still a possibility that it will happen eventually. This leads on to a very interesting question: What’s stopping this happening?

In other words, if the law of very large numbers makes it highly likely that diseases will spontaneously generate the mutations needed to spark a global epidemic, why are they so rare? If we can work that out, then we could hopefully move towards stopping those that do occur. Here, I’m not talking about a zombie apocalypse, but real world problems, like HIV, flu, ebola, SARS and MERS, and others which we’ve still yet to discover, and which have the power to destroy large proportions of humanity if and when they go pandemic. What makes these diseases suddenly appear as if out of nowhere and start running riot through human communities and populations, while others, like rabies, simply remain bubbling away slowly in the background? This isn’t just idle speculation, but something which is fundamental to our understanding of diseases, and indeed our future on this planet.

Who would have thought that’s where we’d have ended up when we started trying to work out if zombie apocalypse preppers were wasting their time or not?


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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.

Real ‘Zombie’ Diseases

21 Nov

Many zombie-type stories start with an outbreak of a disease that either turns living people into violent maniacs (think of the rage virus in 28 Days Later), or converts them into the walking dead (as is the case in World War Z). These diseases are fictional, but there are real ones out there that are just as scary and that share many of the same traits as any zombie infection.  They may get passed on through bites and frequently they’ll hack into your brain, gradually taking it over and, in some cases, making you do things that you wouldn’t normally do. In this article, I’m going to introduce you to three of these ‘zombie’ diseases. You might think these are obscure diseases only found in far-flung rain-forests but, depending on where in the world you live, you’re likely to find one, and possibly all three, can be caught within easy walking distance of your own home, or even inside it. This is something I can say with certainty from first-hand experience as I’m currently being treated for one of them.

Tick Bite Rash

The rash radiating out of a tick bite on my leg that is the early signs that the bacteria which causes Lyme Disease is starting to take over my body (and, if I don’t do something about it, eventually my brain!).

So I’ll start with the one I currently have.  This is Lyme Disease, named after a town in Connecticut and only discovered in the 1970s.  This is an insidious little disease. It’s spread through tick bites (that’s how I picked it up), and often starts with classic flu-like symptoms and a rash that radiates slowly away from the bite site.  It’s strange watching, as I have done for the last week, the rash spread over several days, as the infection works it’s way through your flesh (I can’t help but be reminded of a festering bite from a zombie whenever I look at the one currently spreading across my leg).  Then the rash goes away and all seems fine. It’s only months, or sometimes years, later that the real problems kick in. This can be chronic fatigue, muscle weakness and paralysis, turning you into a shambling, groggy zombie.  The strain you get in Europe also has a tendency to get into your brain, causing neurological problems. Luckily it’s easily treated, at least in the early stages, and a two-week course of antibiotics is enough to rid your body of the bacteria that cause it. Later stages are more difficult to treat, but it’s still treatable none the less.

The next disease I want to consider is rabies.  Rabies is something that in western countries has pretty much been eliminated (although it is making a comeback in some places as wildlife re-invades our cities and homes), and we’ve forgotten quite what a horrific disease it is. The virus causes those infected with it to produce vast amounts of saliva, causing them to, quite literally, foam at the mouth. This is the disease’s cunning way of getting passed on because the saliva is full of the virus, ready to infect anyone the carrier bites.  It also takes control of the brain, making the infected animal or person do things they wouldn’t normally do.  This includes relentlessly attacking others with little or no fear.  While there’s a vaccine for rabies, this will only work if it’s given before the infection reaches the brain and the victim starts showing symptoms. After that, death is almost a certainly, but only after the infected person has been sent mad, because there’s no treatment, and no cure. Because of it’s terrifying characteristics, including the way it takes over people’s brains, rabies has often been used as an agent to create zombie-like creatures (including my own book For Those In Peril On the Sea). However, real rabies differs from these fictional accounts in that it progresses ever so slowly, taking months, or years in some cases, to kill its victims, and there have been no known cases of human to human transmission.

You might think you’d be safe from animal-borne diseases in your own home, but there’s one we readily invite into our houses, or at least people with cats do. This is toxoplasmosis. At first, toxoplasmosis mightn’t seem like a zombie disease, but once you find out what it does, and why, you’ll see why I think it is.  Toxoplasmosis is caused by a protozoan parasite. It’s main host is cats, either of the domestic or big variety, and it does them little harm.  Why would it? It needs its cat host to be healthy so it can survive.  However, the offspring are passed out in the cat’s faeces, and this is where humans can pick it up, especially when cleaning out litter trays. While it can cause serious problems to people with weakened immune systems, it’s most insidious effect comes in otherwise healthy people.  In them, it can form cysts in the brain that will sit there, apparently doing nothing. These cysts are surprisingly common and can be found in ten percent or more of the human population. Experiments have shown that rodents infected with toxoplasmosis become fearless, even approaching cats rather than running away from them.  If you think about this from the parasite’s point of view, fiddling with the rodent’s brain like this is the perfect way to ensure that it ends up back where it wants to be. That is inside a cat. Yet, there is evidence (equivocal I’ll admit, but it’s still interesting) that toxoplasmosis affects humans in a similar way, making them more reckless.  Why would it do this?  Well, if you think back a few hundred thousand years to a human on the plains of Africa, this would be the perfect behaviour to ensure someone was eaten by a big cat, so completing the circle of life (at least from the parasite’s point of view!).

So here we have three real diseases, each of which has elements of the fictional zombie diseases used in so many books and movies. Two are spread through bites, all will infest your brain if given have a chance and will change how you think and behave, and one (Rabies) turns you into something so similar to the zombie-type infected of 28 Days Later that it’s truly frightening. In fact, the only real difference between these real diseases and the fictitious ones is the rates at which they spread.  Almost all are slow-acting, taking weeks, months or years to take over your brain, and none have the virulence of the fictional ones. But, just think what would happen if, for some reason, this were ever to change?

If you’re interested seeing a bit more on this subject, here’s some links to some follow-up videos:

This link shows how little fear a rat infected with toxoplasmosis has for cats (in this case going as far as attacking it!):

These two links are more about possible links between toxoplasmosis and zombie outbreaks:



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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.

Odd Things I’ve Learned While Researching My Books

26 Oct

1. Rabies travels along nerves to the brain at a very specific and standardised speed. This means that the time it takes to affect people is dependent on where on the body they’re bitten. It takes longer to affect people if their bitten on the hand or the toe than if they’re bitten on the face.

2. Large fires can create their own weather in terms of wind, rain, and lightening. Together these are known as a fire storm. There’s even a type of cloud called a Pyrocumulonimbus that only occurs over such fires.

3. If someone has a tension pneumothorax, in an emergency you can save their life using a bottle, a tube and the outside of a biro. A Doctor once did this to someone on a flight from Asia to the UK using stuff he borrowed from the other passengers.  I hope these were washed before he returned them!

4. A tension pneumothorax is when some one has a burst lung and air becomes trapped between the lung and the body cavity. It can kill you if not sorted out soon enough (such as by doing number 3!)

5. In the official King James version of the bible, unicorns are mentioned nine times (don’t ask what I was looking for when I came across this one, sometimes you just get side-tracked!).  This has been edited out of the more recent interpretations, but you will find it in the older ones.  If you have a copy to hand, try looking at Isaiah 34:7.  If it mentions Unicorns you have an older copy.  If it doesn’t, it’s one of the newer versions where the reference to unicorns has been removed – presumably because, unlike in the 17th century when the King James edition first came out, we now know that unicorns don’t exist and it made a mockery of anyone claiming that the bible was the absolute word of God.  Yet, if it has been revised and edited to remove any awkward references….


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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 the UK. Click here or visit www.forthoseinperil.net to find out more.