The Rules of Contagion summary

The Rules of Contagion is the best book to read if you want to understand how ideas and viruses spread. Given the Covid-19 pandemic, it’s a phenomenon we could all do with understanding a little better.

Contagion is when ideas or a virus rapidly spreads. In the context of a pandemic, it’s when a virus spreads from one person to another to the extent it has crisscrossed the globe, increasing exponentially initially.

This is what happened during the Covid-19 pandemic. But it’s also what happens online. If you’ve used Twitter before, you’ll understand this phenomenon. There’s a reason we refer to something which spreads rapidly on the internet as ‘viral.’

The author, Adam Kucharski, works in epidemiology and is a useful guide through the book as he breaks down the concept of contagion and makes it easier to understand for the layperson.

Once you’ve read the book, you’ll have a better understanding of why we were placed under restrictions during the pandemic and why someone like Donald Trump garnered the attention he did on Twitter.

My The Rules of Contagion summary will break down the key points from this fascinating book and help you to understand how ideas and viruses spread.

The Rules of Contagion summary

  • 1-sentence summary: The Rules of Contagion looks at how viruses and ideas spread and the underlying rules which cause them to proliferate.
  • Author: Adam Kucharski
  • Year published: 2020
  • Pages: 346
  • Rating: 8/10

Takeaway 1 – Ideas about contagion don’t always correlate to reality

One of the most interesting things I learnt from reading Pale Rider, Laura Spinney’s account of the Spanish flu, was little people knew back then about infectious disease.

At that time, they weren’t aware that a virus caused flu. A more common explanation was miasma or bad air. One hundred years after this pandemic, we know much more about viruses spread and how to stop them.

But this look at our recent past does reveal a key point. For as much as we do know, there’s always more we’re yet to learn.

It’s only in recent history, we’ve learnt how viruses spread. Previous generations put the spread of disease down to miasma or divine intervention.

Why is this important today?

Well, during the Covid-19 pandemic, there were still a lot of people who were downplaying the virus. Even agencies such as the World Health Organisation (WHO), got their advice wrong when it came to masks.

Then, there are the politicians such as Donald Trump and the Brazilian President, Jair Bolsanaro, who didn’t believe the virus was dangerous at all. This is despite both of them contracting the disease.

We know more than ever about viruses and the impact of letting a novel virus spread across the planet. But we’re still susceptible to the foolishness of those who lead us.

For all the progress we’ve made in the scientific arena, it’s the political arena which can lead to deadly consequences if politicians don’t heed the advice of medical experts.

Takeaway 2 – Ideas spread just as fast as viruses

If you’ve been on the internet for long enough, you’ll know all about viral content. For anyone that’s unaware of the term, here’s a quick overview.

Viral content is content that gets a lot of views and shares in a short space of time. Think of a song on YouTube that gets shared by everyone, or an article that everyone is talking about.

The more people who read and share it leads to an ever-greater number of people doing the same until it peters out, much like the initial stage of a disease-related epidemic.

The difference with viruses is that ideas don’t require close contact to spread. Think of Covid-19. If everyone is meeting up with one another and not taking precautions, the virus is going to spread like wildfire.

Whereas, with mitigation such as mask-wearing and lockdowns in place, it’s much harder for the virus to spread from person to person.

Ideas don’t have these barriers. Yes, they require people to share, but it’s much easier to do this on the internet. All it takes is one prominent person to share an article or a video for it to go flying around the internet.

It could even be argued ideas spread faster than viruses. Such is the speed with which fake news can spread around the globe, that might be true.

Takeaway 3 – Getting things wrong helps you to get them right

One of the curiosities of the Covid-19 pandemic has been watching various people, mainly on Twitter, criticise health experts for being wrong earlier in the pandemic.

The mask guidance is one example. Looking back, it looks ridiculous they weren’t recommended earlier in the pandemic. Of course, hindsight is 20-20 and what looks obvious now wasn’t so at the time.

It’s important to remember Covid-19 was a novel virus ad not much was known about it. There were bound to be things epidemiologists and others got wrong. No one is infallible.

Taking positions such as these might seem helpful, but they’re often not. We learn from failure. It’s how we improve and make progress.

To attack people for getting things wrong is ludicrous because we’ll all get things wrong at some point. There’s no linear path to the right answer, it’s a bumpy road full of ups and downs.

This is true in epidemiology and many other fields. You often have to sift out the wrong answers to find the right one.

Condemning people with the power of hindsight is dangerous and disingenuous.

Favourite Quotes

  • “When it comes to contagion, history has shown that ideas about how things spread don’t always match reality. Medieval communities, for example, blamed the sporadic nature of outbreaks on astrological influences; influenza means ‘influence’ in Italian.”
  • “According to SIR model, outbreaks need three things to take off: a sufficiently infectious pathogen, plenty of interactions between different people, and enough of the population who are susceptible. Near the critical herd immunity threshold, a small change in one of these factors can be the difference between a handful of cases and a major epidemic.”
  • “R therefore depends on four factors: the duration of time a person is infectious; the average number of opportunities they have to spread the infection each day they’re infectious; the probability an opportunity results in transmission; and the average susceptibility of the population. I like to call these the ‘DOTS’ for short. Joining them together gives us the value of the reproduction number: R = Duration x Opportunities x Transmission probability x Suspectibility”
  • “If we want to predict a person’s risk of infection, it’s not enough to measure how many contacts they have. We also need to think about their contacts’ contacts, and their contacts’ contacts. A person with seemingly few interactions might just be a couple of steps away from a high transmission environment like a school.”
  • “Using public health approaches to prevent crime would be hugely cost-effective, both in the US and elsewhere. Adding together, the social, economic and judicial consequences of the average US murder, one study out the cost of a single killing at over $10m. The problem is that the most effective solutions may not be those people are most comfortable with. Do we want to feel like we’re punishing bad people, or do we want less crime?”

The Rules of Contagion review

The Rules of Contagion is a fantastic book that will teach you the underlying principles of why things spread. It’s a pure coincidence the book was published at the same time a pandemic took off, but it’s a timely one nonetheless.

If you’ve been confused by what’s happened during the pandemic and baffled at some of the decisions taken, this book will help you make sense of it all.

It’s an easy to understand guide to how contagion works and why it can lead to situations like the one which unfolded in the early parts of 2020.

I found it to be a fascinating and helpful book. It put together all of what I’d learnt during the course of the pandemic and helped me to understand it all.

For the average person, it was a bizarre time. The human brain tends to like simplistic answers to complex problems as it helps us to come to terms with the fact we live in a chaotic world.

But as Nassim Taleb demonstrates in The Black Swan, that’s not the case. The world is much more complicated than we realise.

I can’t think of many books better to help you understand why infectious viruses and ideas spread the way they do. The Rules of Contagion is a must-read if this is what you want to learn.

Who should read The Rules of Contagion?

Anyone who is interested in understanding how viruses spread or learning more about contagion will gain a lot of value from The Rules of Contagion.

It’s arguable everyone should read this book, especially after living through the Covid-19 pandemic. Understanding how viruses spread and what it means for us is a great way to arm yourself with the information you need during a disease outbreak.

I think all of us were caught by surprise when Covid struck. Understanding what causes contagion and how we can mitigate this, will stand us in good stead going forward.