Why things go VIRAL and why the world goes mad when they do



By Adam Kucharski (Wellcome Collection £16.99, 352 pp

Were there a Booker Prize for timeliness, this nuggety gem of a book would be a shoo-in. But don’t think this is an opportunistic (or a simply lucky) attempt to ride on the back of the coronavirus pandemic.

The opposite: the book was finished before anyone had even heard of Covid-19, and the manuscript was being prepared for publication as reports were emerging of the very first few cases.

Internet craze: Simon Cowell braves the cold in the Ice Bucket Challenge on a boat in 2014

In an act of masterly self-denial, Adam Kucharski, a mathematically trained epidemiologist at the London School of Hygiene & Tropical Medicine, resisted any temptation for last-minute updates on the new epidemic.

Just as well — coronavirus is developing so ruthlessly, anything Kucharski wrote about it would be out of date by the time it was published.

Instead, he has given us an astonishingly bold survey of, well, the epidemiology of more or less everything in our inter-connected world.

He looks at the links between outbreaks of physical disease, computer viruses, stock market bubbles, the growth of folk legends, online influence, patterns of behaviour, drug addiction, obesity, gun and knife violence, even why internet games come and go (remember the ice bucket challenge?).

And the book provides the ideal backdrop to attempting to understand what is going on today.

There’s some maths in here, sure, but please don’t let that put you off. Trust me.

The flu epidemic which began at a military base in Kansas towards the end of World War I would eventually kill more than 50 million people, with the final death toll twice as high as the entire war.

The cause was a new type of influenza virus, which had potentially jumped from animals to humans at a farm nearby.

There would be four more flu pandemics over the next 100 years. But each looks different. Hence, the problems over our current epidemic. As Kucharski writes: ‘There’s a saying in my field: “If you’ve seen one pandemic, you’ve seen . . . one pandemic.” ’ And like all good mathematicians, he knows that numbers are the key. Not hysteria. Not fear.

Adam Kucharski reveals why outbreaks and information spread and fade away at bewildering speed. Pictured: A woman wears a face mask while walking in London

Adam Kucharski reveals why outbreaks and information spread and fade away at bewildering speed. Pictured: A woman wears a face mask while walking in London

An early pioneer was an Indian Army doctor called Ronald Ross, who worked out there was a link between mosquitoes and malaria.

The disease is one of the oldest known to man, and its name comes from medieval Italy, where a fever would be blamed on ‘bad air’ — mala aria.

Ross, who won a Nobel Prize for his work, realised you didn’t have to wipe out every mosquito to eliminate malaria, just enough — by limiting disease-ridden standing water and other practical acts — to provide some sort of immunity.

He built a mathematical model to show that infection and transmission would die out once the mosquito population dropped. The disease has been controlled since the Fifties.

The shape of all outbreaks is roughly the same: first spark, then growth, peak and decline. It is a pattern known as the SIR model, dividing populations into three types: susceptible, infected and recovered.

Once the number of recovered people is large enough, the disease will die out as there is no one left to infect.

And at the heart of that is a mathematical big beast, the reproduction number, known as R, representing the number of people an infected person will go on to infect. If R is less than one, then sooner or later the disease will die out.

But above that, if R is greater than one, the contagion will spread. The R for coronavirus appears to be between two and three, comparable to the Sars outbreak of 2002.

Ebola and pandemic flu have an R between one and two.

Measles, though, which is staggeringly infectious, has a very big R, about 20.

Which in turn makes the careless insanity of the anti-vaccination movement all the more criminal. That pernicious campaign is a perfect example of the evils of online contagion.

So while all current efforts — containment, reduction in social contact, treatment and, ideally sooner or later, vaccination — are devoted to limiting and reducing the R of coronavirus, the strain will die out only once we get its R below one.

Kylie Minogue completes the ALS Ice Bucket Challenge alongside her friend Stefano Gabbana

Kylie Minogue completes the ALS Ice Bucket Challenge alongside her friend Stefano Gabbana

By the same token, if you run an online business or want to promote something, you obviously want an R that is as high as possible. Facebook reported that its fastest propagating online content was the 2014 ice-bucket challenge, with an R of two or so. But this peaked suddenly and died out naturally, because most of the participants were part of a friendship group, and eventually it ran out of people.

Kucharski is especially good on the role of the individual, and this is a richly anecdotal book.

As HIV — with its initially mysterious routes of infection and transmission — cut swathes through sections of the population all over the world in the Eighties, a very important moment happened on April 19, 1987. Princess Diana opened a new Aids treatment unit at the Middlesex Hospital in London and, while there, she did something that surprised even the hospital staff: she shook a patient’s hand.

The effect was immediate and hugely significant because, despite scientific evidence that HIV could not spread through touch, there was a popular belief that it could. The princess’s act changed all that.

HIV, like smallpox, has an R of around five, which makes the medical campaign that has practically stamped out its fatalities all the more remarkable.

As we live through the throes of a disease pandemic and a stock market panic, never has it been more important to hold the line between real and bogus information.

It’s not a new phenomenon. In Evelyn Waugh’s 1938 satirical novel Scoop, legendary American foreign correspondent Wenlock Jakes is sent to cover a revolution in the Balkans.

Unfortunately he oversleeps on his train and wakes up in the wrong — but wholly peaceful — country. Not realising his error, he makes up a story about ‘barricades in the streets, a dead child like a broken doll spreadeagled in the deserted roadway, machine guns answering the rattle of his typewriter’.

Other journalists swiftly arrive and make up similar stories, stocks plummet, the country has an economic crash, there’s a state of emergency, and then a revolution. And Jakes is there to cover it.

Fiction of course, but now the speed at which bogus information can be transmitted — like a virus — is incomparably quicker than in Waugh’s day.

Whether it is disease epidemics or crime and terrorism, mathematical models can help countries plot outcomes and allocate resources.

But models are just that, writes Kucharski: reality is messy and complex. If you build a model train set — no matter how skilful and full of add-ons such as delays, leaves on the line, faulty signals — it will always differ from reality in some way.

There was some post-9/11 research into threats from bioterrorist attacks, which put possible fatalities at 77 trillion. Not bad for a world population of seven billion.

The word coronavirus doesn’t crop up in this brilliant, dense, scholarly book. But Kucharski has pulled off the extraordinary trick of shining the brightest light, for this reader anyway, on this unseen, menacing, but ultimately beatable, enemy.