The Ghost Map: The Story of London's Most Terrifying Epidemic - and How It Changed Science, Cities, and the Modern World by Steven Johnson is an excellent nonfiction read for anyone who enjoys history, especially the history of science. It tells the story of an outbreak of cholera in Victorian London, and how two men from different backgrounds and points of view fought the prevailing - and dangerously wrong - view of the disease. Although I had never heard of this story, it is apparently well known, and usually mistold; The Ghost Map corrects some common misconceptions.
In Victorian England, one misconception was very great, and it was deadly. People believed that cholera - and most disease - was spread through something called "miasma," meaning bad air. In short, if you could smell it, it could kill you. And boy, could you smell it. Don't read The Ghost Map while eating! It is full of rich, detailed descriptions of the stench and filth of Victorian London, a city whose population had mushroomed into the largest city ever known on our planet, but whose sanitation methods had not begun to catch up. The descriptions of outhouses and cesspools emptying directly into the Thames, while children bathed and drew drinking water only a few meters away, is positively stomach-turning. And the detailed description of cholera itself - how the disease spreads, how its victims suffer and die - is equally and fittingly disgusting.
But in 1854, the concept of micro-organisms that were invisible to the human eye living in and poisoning water was not yet understood. Since disease was spread by foul air, or so the story went, public health would be improved by making the air fresher and better smelling. The solution: move all the human and animal waste into the river, where it will be carried away.
In a few decades the Thames was transformed from a clean river full of salmon to a giant, festering sewer drain. The advent of flush toilets - which emptied ten times as much water into the river - made it ten times worse. Thus, Johnson shows, the first great public works of London had the effect of poisoning the population.
The miasma theory of disease was riddled with gaping holes. If smelly air caused cholera, then the people who worked in London's sewers - urban scavengers who spent their days combing through human excrement - should be the sickest people of all. Yet they were generally healthy and lived to what was then old age.
If smelly air caused cholera, why did people in grand mansions, where the chamber pots were emptied immediately and the air smelled fresh, succumb to the disease as often as the destitute who lived right near the smelly river? These inconsistencies were explained away with a combination of superstitions and medieval beliefs. The waterborne theory of disease was ignored or ridiculed.
John Snow, an accomplished doctor and inventor, believed cholera was spread by water. Snow didn't have the tools to prove his theory through direct observation. So he went about proving it indirectly, by painstakingly documenting outbreaks of the disease, looking for patterns and making connections between the water residents drank and the illness. (As it turns out, the cholera bacteria had been isolated and identified by a scientist in Italy, but that breakthrough had been ignored.) London was built on a crazy labyrinth of water and sewer pipes, and a dozen different companies provided the city with water. Snow faced a monumental job - and along the way, he became the first person to map an epidemic. His methods and the map he created form the basis of the modern methods of understanding and controlling infectious diseases.
John Snow was right, but no one was listening. Henry Whitehead was a minister with deep roots in the London community that was being devastated by cholera, and he became Snow's crucial ally. Like everyone else, Whitehead originally subscribed to the "miasma" theory, but his open mind and intelligence compelled him to accept Snow's waterborne theory. Johnson demonstrates how Whitehead's deep understanding of the neighbourhood was the link to the eventual ascendancy of Snow's theory: how the local impassioned amateur works with the trained scientist both to reach the necessary conclusion and to make people hear it. He also shows how urban life itself contributed to the understanding that eventually stopped the outbreak: "the battle between metropolis and microbe was over, and the metropolis had won."
Cholera would continue to terrorize Western cities into the first decades of the twentieth century, but with London's successful engineering project as a model [i.e., the building of London's monumental sewer system], the outbreaks usually prodded the local authorities into modernizing their civic infrastructure. One such outbreak hit Chicago in 1885, after a heavy storm flushed the sewage collecting in the Chicago River far enough into Lake Michigan that it reached the intake system for the city's drinking water. Ten percent of the city's population died in the ensuing outbreak of cholera and typhoid, and the deaths ultimately led to the city's epic effort to reverse the flow of the Chicago River, sending the sewage away from the water supply. . . . By the 1930s, cholera had been reduced to an anomaly in the world's industrialized cities. The great killer of the nineteenth-century metropolis had been tamed by a combination of science, medicine, and engineering. In the developing world, however, the disease continues to be a serious threat. A strain of V.cholerae known as "El Tor" killed thousands in India and Bangladesh in the 1960s and 1970s. An outbreak in South America in the early 1990s infected more than a million people, killing at least ten thousand. In the summer of 2003, damage to the water-supply system from the Iraq War triggered an outbreak of cholera in Basra. There is a fearful symmetry to these trends. In many ways, the struggles of the developing world mirror the issues that confronted London in 1854.The Ghost Map is at its best in the history and sociology of science department, tracing the solving of a medical mystery. Johnson goes beyond the history to make links between that long-ago cholera outbreak and our contemporary world. He is a passionate urbanist, who correctly believes that cities are good for humans and good for the planet. He quotes the great urban activist Jane Jacobs and writes about the giant so-called squatter cities now occupying - and in some respects, thriving and developing - in places like Mumbai and Sao Paolo. He has great hope for these situations, tempered with great caution.
Johnson concludes by writing about the modern descendants of John Snow's disease-mapping techniques, both the high-tech tools of the Center for Disease Control and the local geomapping of urban neighbourhoods through popular online tools. He speculates about the threats of biological or nuclear terrorism, to which an urban population is at much greater risk than a widely dispersed population. He also mentions that if humans don't deal effectively with both climate change and our dependence on fossil fuel, our long-term prospects are not good.
Johnson goes far afield, and you may or may not agree with his conclusions, but he writes strongly and convincingly. However, it's the first two-thirds of The Ghost Map that are most fascinating. (This review was originally published here, on wmtc.)