Sleuths on the scent of a superbug

Published on 19/11/2006 01:22

The Ghost Map

Steven Johnson

Penguin: Allen Lane, 16.99

AT THE end of a sweltering August 1854 in Broad Street, Soho, London, a baby had diarrhoea. A fortnight later, nearly 700 people who lived within 250 yards of the child's home had perished. A tenth of the population of Broad Street died, and only four of the 45 adjacent houses completely escaped any mortality. It was perhaps the most virulent outbreak of cholera the city had ever witnessed, and The Ghost Map tells the story of the two men who, against the prevailing scientific wisdom, identified the source of the infection and prevented the further spread of the epidemic.

One of them was Dr John Snow, a brilliant anaesthetist, who had risen from humble origins to treating Queen Victoria. He was diffident, teetotal, vegetarian and was subjected to outraged denunciations in the pages of the newly formed medical journal The Lancet. The other was a conscientious, open-minded, sociable young clergyman, the Rev Henry Whitehead, who spent those awful weeks in September tending to the families decimated by the disease.

It is a rattling scientific mystery: but in the hands of Steven Johnson - author of Everything Bad Is Good For You and, more importantly, Interface Culture and Emergence - it becomes something much richer. Through the keyhole of Snow and Whitehead's quest to counter the cholera outbreak, Johnson shows the reader a vast, interconnected picture about urban and bacterial life: how information and illness spreads, how ideas and sewage flow; in short, the whole ecosystem of what a city 'means'. The Ghost Map is not just a remarkable story, but a remarkable study in what we might learn from that story.

Part of its success is in the detailed context that Johnson provides. In 1854, as detailed in Henry Mayhew's classic London Labour And The London Poor a decade earlier, there existed a substantial underclass of scavengers, bone-pickers, mud-larks, pure-finders, night-soil-men and crossing-sweepers. In one of the salient comparisons that enrich Johnson's text and the reader's understanding, he notes that if they had all been relocated out of London they would have formed the fifth biggest city in England. Their purpose in the metropolis was simple, if unsavoury. Someone had to deal with all the filth.

LONDON WAS an industrial-age city with medieval waste-disposal. It wasn't just open drains and overflowing cesspools: in some properties the cellars were waist-deep in excrement. Yet, in one of the paradoxical virtuous circles that Johnson specialises in, the transportation of this dung to the countryside had enhanced the fertility of the soil, and meant that the city's increased food requirements could be met.

Nonetheless, the sanitary conditions were a problem. There had been cholera scourges beforehand, and the prevalent orthodoxy had it that the cause was "miasma" - or, more bluntly, fetid, airborne stench. By a combination of rationalism and local knowledge, Whitehead and Snow traced the very water-pump that had been infected, even "Case Zero" - the sickly child whose nappy had seeped into the drinking water.

Why did the miasma theory, against all evidence, enjoy such support? Johnson doesn't offer a single cause, but a cluster of "overdetermined" factors. There was the classical precedent of Hippocrates, and the unthinking conservatism that aligned poverty with pestilence. Perhaps most important, however, was involuntary instinct. Human noses may not be on a par with dogs', but they are astonishingly sensitive organs, and they are hardwired into a very old part of our brains. There is an evolutionary advantage in just gagging at foul smells - it protects us from ingesting infected or decaying matter. Cholera, ironically, was historically slow to spread because the idea of swallowing effluent is unthinkable. Bad smells were obviously bad. A few parts diluted in a million could go undetected.

Snow's challenge was that the answer was as invisible as the stinks were clear. On one hand, the bacteria were microscopic. Infected water looked perfectly transparent. On the other, the city-wide distribution pattern of fatalities was just as difficult to visualise. Only by painstaking work and door-to-door enquires did the true picture emerge.

The ghost map of the title refers to the ingenious way Snow represented his data - a method now referred to as a Voronoi diagram. All cities have shortcuts as well as cul-de-sacs, and Snow cleverly mapped the walking proximity to the infected water-pump. You might be close to it as the crow flies, but a good schlep away by foot. In this, Whitehead's parish experience was invaluable. He knew how his parishioners went about their business. Johnson here sees a link to the "new localism" of the internet, where amateurs, rather than corporate planners, can best reflect a particular district's concerns, highlights and character.

The lessons Johnson derives from Whitehead and Snow's successful investigation are manifold. In the 19th century, the very idea of having more than two million people living in a space of 90 square miles seemed irrational. Now it's normal. What was at stake with cholera, to its contemporaries, was not so much staying alive in the city but whether or not cities were even capable of sustaining life.

On a pragmatic level, Whitehead and Snow paved the way for practically liveable cities. They also, according to Johnson, revealed a more "emotional" level to urban living. Two strangers, outwardly very different, one a man of science and the other of faith, became friends. London, for all its grime and grief, was still a place where new possibilities could occur. Johnson gives a stirring defence of city life - ecologically, socially, in terms of health, in terms of opportunity.

It may be one of the more contentious points in the book, but there is a certain logic behind the idea that if we wish to preserve natural ecosystems, more people will have to live in cities. The footprint of cities, however, depends on very old-fashioned mathematics of scale. Disperse the population of Portland across the state of Oregon, and you'd need 5,000 miles more of pipes, and 100,000 septic tanks. Congregation may be better than a return to nature.

It is not a wholly rose-tinted view. By 2015, the largest cities will be Tokyo, Mumbai, Dhaka, Sao Paulo and Delhi, and the scientific endeavour required to turn the 'shadow cities' of squatters and shanties into viable residences will be equal to Snow and Whitehead's. Johnson also addresses the problems of terrorist threats, avian flu and other biological hazards, but reserves his chief anxiety for old-fashioned nuclear explosions.

It is difficult to do justice to the exuberance of Johnson's ideas, or to his uncanny knack of finding connections and parallels between the most diverse and esoteric disciplines. The Ghost Map is a challenging and exciting work which removes historical non-fiction from the heritage industry and puts it back into lively, impassioned debate.