The Rules of Contagion

by Adam Kucharski

  Seeking the Positives: A Life Spent on the Cutting Edge of Public Health by John Potterat (CreateSpace, 2015) gives more details of his work on how social networks shape outbreaks of gonorrhoea and other STDs. For a technical overview of disease modelling, Modelling Infectious Diseases in Humans and Animals (Princeton University Press, 2007) by Matt Keeling and Pej Rohani had been an essential textbook for me ever since I first read it as an undergraduate.

  Andy Haldane’s speech ‘Rethinking the Financial Network’ (Bank of England transcript, 2009) was a timely discussion of the links between ecology, epidemiology and financial markets. His later paper with Robert May, ‘Systemic risk in banking ecosystems’ (Nature, 2011), expanded on these ideas with more technical details.

  Chapter 3

  Connected: The Amazing Power of Social Networks and How They Shape Our Lives by Nicholas Christakis and James Fowler (HarperPress, 2011) describes research into dynamics of social networks, including their studies on the spread of obesity and other characteristics. Their subsequent paper ‘Social contagion theory: examining dynamic social networks and human behavior’ (Statistics in Medicine, 2013) discusses the criticisms of their research, and the technical challenges involved in estimating social contagion. Damon Centola’s book How Behavior Spreads: The Science of Complex Contagions (Princeton University Press, 2018) covers his work on complex contagion, as well as other insights from large-scale studies of behaviour. ‘Randomized experiments to detect and estimate social influence in networks’ by Sean Taylor and Dean Eckles (Complex Spreading Phenomena in Social Systems, 2018) is a useful technical review of approaches for studying social contagion.

  Further insights from the NATSAL studies can be found in David Spiegelhalter’s book Sex by Numbers: What Statistics Can Tell Us About Sexual Behaviour (Wellcome Collection, 2015). ‘Culture and cultural evolution in birds: a review of the evidence’ by Lucy Aplin (Animal Behaviour, 2019) provides an overview of cultural development in animals, with a focus on birds.

  Chapter 4

  For more discussion and case studies about the spread of violence, including contributions from Carl Bell, Gary Slutkin and Charlotte Watts, see the papers published in Contagion of Violence: Workshop Summary, part of the Forum on Global Violence Prevention (The National Academies Collection, 2013).

  Smallpox: The Death of a Disease – The Inside Story of Eradicating a Worldwide Killer by D.A. Henderson (Prometheus, 2009) has a first-hand account of how contact tracing and ring vaccination was deployed to eradicate smallpox. Neil Ferguson and colleagues’ paper ‘Planning for smallpox outbreaks’ (Nature, 2003) covers ways to model smallpox and other emerging infections, as well as their limitations. ‘Avoidable errors in the modelling of outbreaks of emerging pathogens, with special reference to Ebola’ by Aaron King and colleagues (Proceedings of the Royal Society B, 2015) provides a technical description of some potential pitfalls in forecasting infectious disease outbreaks.

  Weapons of Math Destruction: How Big Data Increases Inequality and Threatens Democracy by Cathy O’Neil (Penguin, 2016) highlights the inherent prejudices and biases in many commonly used algorithms, including ones used in policing. Hello World: How to be Human in the Age of the Machine by Hannah Fry (Penguin, 2019) has more on the roles – and risks – of algorithms in modern life.

  Chapter 5

  Duncan Watts’ book Everything is Obvious: Why Common Sense is Nonsense (Atlantic Books, 2011) has some useful insights into the challenges of understanding and predicting social behaviour online. His later paper with Jake Hofman and Amit Sharma, ‘Prediction and explanation in social systems’ (Science, 2017), elaborates on the technical aspects of this research. Justin Cheng and colleagues’ paper ‘Do Diffusion Protocols Govern Cascade Growth?’ (AAAI, 2018) provides a data-driven breakdown of the components of the reproduction number of online content. The Facebook Research archive (https://research.fb.com/publications) has a host of other papers further examining the spread of behaviour and content online.

  Whitney Phillips’s report The Oxygen of Amplification: Better Practices for Reporting on Extremists (Data & Society, 2018) provides a valuable summary of media manipulation efforts, and potential ways to overcome these. Zucked: Waking Up to the Facebook Catastrophe (HarperCollins, 2019) by Roger McNamee discusses the downsides of social media platforms, including more details on the work of Tristan Harris and Renée DiResta. ‘Protecting elections from social media manipulation’ by Sinan Aral and Dean Eckles (Science, 2019) has suggestions for ways to rigorously measure online manipulation and the potential implications for elections.

  Chapter 6

  For more on the origins and legacy of Mirai attack, see Garrett Graff’s pair of articles for Wired: ‘How a Dorm Room Minecraft Scam Brought Down the Internet’ (2017) and ‘The Mirai Botnet Architects Are Now Fighting Crime With the FBI’ (2018). Landmark papers such as ’Computer Viruses – Theory and Experiments’ by Fred Cohen (1984) and ‘How to 0wn the Internet in Your Spare Time’ by Stuart Staniford and colleagues (Proceedings of the 11th USENIX Security Symposium, 2002) have more technical details on the history of viruses and worms. Linked: The New Science of Networks by Albert-László Barabási (Perseus, 2002) describes the history of network theory, including how networks shape malware outbreaks.

  Chapter 7

  ‘Towards a genomics-informed, real-time, global pathogen surveillance system’ by Jennifer Gardy and Nick Loman (Nature Reviews Genetics, 2018) reviews how sequencing tools can be used to diagnose and track diseases. ’Outbreak analytics: a developing data science for informing the response to emerging pathogens’ (Philosophical Transactions of the Royal Society B, 2019) explores the uses of data science during outbreaks, as well as areas for improvement.

  Anthony Tockar’s original two Neustar blog posts, ‘Differential Privacy: The Basics’ and ‘Riding with the Stars: Passenger Privacy in the NYC Taxicab Dataset’, are worth reading for a more detailed description of the New York Taxi analysis and its implications (available from: https://research.neustar.biz). Bit By Bit: Social Research in the Digital Age by Matthew Salganik (Princeton University Press, 2018) provides a thoughtful overview of the ethical and logical issues involved in modern social behaviour research.

  Chapter 8

  David Sumpter’s book Outnumbered: From Facebook and Google to Fake News and Filter-bubbles (Bloomsbury, 2018) assesses the statistical plausibility of claims about online algorithms, with a particular focus on the Cambridge Analytica scandal. Getting to Zero: A Doctor and a Diplomat on the Ebola Frontline by Sinead Walsh and Oliver Johnson (Zed Books, 2018) gives a first-hand account of the politics, logistics and human cost involved in responding to the West Africa Ebola epidemic.

  Acknowledgements

  I’d like to thank everyone who took the time to share their expertise and experience with me while researching this book: Lucy Aplin, Nim Arinaminpathy, Wendy Barclay, Barbara Casu, Nicholas Christakis, Toby Davies, Dean Eckles, Paul Fine, Jemma Geoghegan, Andy Haldane, Heidi Larson, Rosalie Liccardo Pacula, Kristian Lum, Brendan Nyhan, Andrew Odlyzko, Whitney Phillips, John Potterat, Charlie Romford, Gary Slutkin, Briony Swire-Thompson, Jamie Tehrani, Melissa Tracy, Alex Vespignani, Charlotte Watts, and Duncan Watts. Thanks also to those who helped source historical data and documents: Victoria Cranna and Alison Forsey at the LSHTM Library & Archives Service, Liina Hultgren at the Royal Institution, and Peter Vinten-Johansen at the John Snow Archive and Research Companion. If there are any errors in the final text, they are mine alone.

  I’ve been fortunate to have had some great mentors during my career, who have encouraged me to engage with wider audiences as well as helping me develop as a researcher: Julia Gog at the University of Cambridge, Steven Riley at Imperial College London, and John Edmunds at LSHTM. Thanks also to many, many other collaborators and colleagues I’ve worked with and learnt from over the years. In particular, the ideas in this book have benefitted both directly and indirectly from discussions with my brilliant colleagues in the Cent
re for the Mathematical Modelling of Infectious Diseases at LSHTM. As any popular science writer will know, I faced the obstacle of there being far more good research out there than I could ever fit into one book. Inevitably, I had to leave out several people and projects during the writing and editing stages, and this is of course no reflection on my views about the quality of the science.

  I’d also like to thank everyone involved in the writing process. My excellent editors Cecily Gayford at Profile and Fran Barrie at Wellcome Collection have provided valuable ideas and input throughout. Thanks as well to Joe Staines for his work on copyediting the finished manuscript. And to my agent Peter Tallack, for his support and advice over the past few years. I am grateful to my parents for all their comments on initial drafts, as well as to Clare Fraser, Rachel Humby, Munir Jahangir, Stephen Rice, and Graham Wheeler for giving feedback on early chapters. Finally, I would like to thank my amazing, inspiring wife Emily, who I was lucky enough to meet while writing my last book, and lucky enough to marry while writing this one.

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