Book Review: The Ghost Map

The Ghost Map by Steven Johnson is a must read for everyone interested in one of the archetypal example of intervention in public health. All public health students know the story, have heeded the call for more shoe leather epidemiology and may also know that removing the pump probably didn’t actually do much to stop the epidemic. Beyond the commonly known facts Johnson gives the reader a true sense of what life was like at the time in London for the poorest classes.
“Above the river, in the streets of the city, the pure-finders eked out a living by collecting dog shit (colloquially called ‘pure’) while the bone-pickers foraged for carcasses of any stripe. Below ground, in the cramped but growing network of tunnels beneath London’s streets, the sewer-hunters slogged through the flowing waste of the metropolis.”
It is evident from the account that John Snow did not act alone and was helped by a number of people, particularly Henry Whitehead a pastor in the Soho neighbourhood of London. Today Soho is one of London’s big party areas with restaurants and bars everywhere. At the time it was one of the poorest areas in the city and living conditions were harsh.
“Imagine if every time you experienced a slight upset stomach you knew there was an entirely reasonable change you’d be dead with forty-eight hours. Remember, too, that the diet and sanitary conditions of the day – no refrigeration; impure water supplies; excessive consumption of beer, spirits, and coffee – created a breeding ground for digestive ailments, even when they didn’t lead to cholera.”
Johnson discusses in detail the scientific discussions of the time and includes some wonderful letters published in the Lancet by Snow and his critics. Interesting to see that the scientific discussion of the day remains much the same today. A discussion that boils down to, how do we construct (or estimate) an appropriate counterfactual? Remember that the randomized controlled trial was only just being developed.
In his conclusions Johnson does a great job describing the cities of the time and making parallels with modern day urban slums in the world’s mega-cities.
“The scavenger classes of Victorian London have been reborn in the developing world. There are a billion squatters on earth now, and some estimates suggest that their numbers will double in the next twenty years.”
My main critique of the book is not with the story itself but rather with the Epilogue. Johnson does his story a disservice by projecting the story John Snow, a story of urbanization and the spread of infectious diseases, onto what I can only call fear mongering about urbanization and biological warfare. If you ask me read the book but skip the Epilogue.
For more on John Snow check out: The John Snow Archive and Research Companion

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