Why things GO VIRAL

From pandemics to the ice bucket challenge ... ... and why the world goes mad when they do

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.

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Just as well — coronavirus is developing so ruthlessly, anything kucharski wrote about it would be out of date by the time it was published.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

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 diseaseridden 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 antivaccination movement all the more criminal. That pernicious