The Rules of Contagion

Adam Kucharski

Allen & Unwin

Otago Daily Times, June 27th 2020

In show business, timing, as they say, is everything. So, too, it would seem for publishing. On the face of it, a book explaining why diseases spread and why they stop would seem to be perfectly placed to appeal to an audience newly conversant in such concepts as R₀, exponential growth and chain of transmission. And in many respects Adam Kucharski’s accessible and broad-ranging disquisition on ways in which the transmission of ideas, news, innovation and misinformation resembles that of an infectious disease is ideal reading for the thousands of amateur epidemiologists the Covid-19 crisis has spawned.

Subtitled Why Things Spread – and Why They Stop, the book begins with a brief history of pandemic modelling and an outline of the factors governing the rate and extent of an infectious outbreak, then describes how these same concepts can be used to understand – and influence – the spread of everything from new technologies to cat memes. It had never occurred to me, for example, that the trajectory of a financial bubble is very similar to that of influenza. I had no idea that the Bank of England called on disease researchers to advise them on how to prevent a recurrence of the 2008 financial crisis. The same phylogenetic analyses that enable researchers to determine a virus’s origin and spread by looking at changes in its genetic code have been used to trace the evolution of language and fairy tales. And just as health authorities might vaccinate those exposed to infection, sociologists in Chicago have developed programmes that identify people at risk of ‘catching and spreading’ gun violence (often former prison mates of the victim) and used mediation to bring down the city’s disastrously high rate homicide rate.

Disease modelling can also be used to determine how infectious particular ideas and behaviours are, research that in our increasingly online world is easier and more important than ever. It is reassuring to know that the influence of fake news on people’s beliefs is considerably less than one might think, less so to discover that they can have a significant effect if picked up by mainstream news outlets. The masses of data generated by our increasingly networked existence provide fertile ground for research and exploitation alike, and future studies must be carefully designed and transparent lest the public become unwilling to participate in studies that could advance physical and social well-being.

Authoritative and rigorously scientific (the final 80 pages are given over to notes and references), Kucharski draws on his own experiences tracking Zika and Ebola to explain how understanding the causes of past outbreaks can inform our responses in the future, only to find his book overtaken by events. COVID-19 perfectly exemplifies every epidemiological principle it describes. I wish the author had been able to update it before publication, not least because I would love to see his analysis of the first truly global pandemic in a century. In the meantime, I must content myself with the knowledge that this, too, will pass, while the lessons it has to teach us will (hopefully) remain.