Plotting death

IF every great city resembles a living organism, then mid-19th century London was an ungainly and careless youthful giant with appalling personal habits. As Steven Johnson makes nauseatingly clear in the grim and gripping early pages of “The Ghost Map,” the stench of human excrement was everywhere.

Forget about sanitary engineering and the modern science of waste management. In the 1850s, the world’s largest city didn’t have a functional sewage system. In addition to home cesspools, backyards and basements were often used as dumping grounds. The widespread use of the water closet only made things worse: Human waste was thoughtlessly flushed from these indoor toilets directly into the River Thames, fouling the city’s drinking water source beyond measure. Unsurprisingly, infectious diseases thrived in such an environment: smallpox, measles, scarlet fever and, most devastating of all, cholera.

“The Ghost Map” charts the London cholera epidemic of 1854, from which Johnson extracts a saga of human ingenuity and true communal effort. Tellingly, no single savior or miracle worker emerges from the ordure. He shows how “the connectors and entrepreneurs and public characters who make the urban engine work at street level” saved the city from itself. Indeed, the seeming chaos and deep interconnectedness of urban life, the very conditions that create an epidemic, can also contribute to its cessation or cure, he writes.

If your cesspool was overflowing, you called the “night-soil men,” a new class among the recyclers who emerged to remove the waste to outlying farms as London’s population swelled. “We’re naturally inclined to consider these scavengers tragic figures, and to fulminate against a system that allowed so many to eke out a living by foraging through human waste,” Johnson acknowledges. “But such social outrage should be accompanied by a measure of wonder and respect: without any central planner coordinating their actions, without any education at all, this itinerant underclass managed to conjure up an entire system for processing and sorting the waste generated by two million people.”

In other ways, the London of 150 years ago will feel oddly familiar to readers today. Johnson records eerie intimations of gentrification: The kind of people we call bohemian now, poets and painters mostly, were moving into Soho, a neighborhood that had been abandoned by the upper classes. “[D]espite -- or perhaps because of -- the increasingly crowded and unsanitary conditions,” Johnson writes, it was “a hotbed of creativity.”

Naturally, the neighborhood was a potential hotbed of disease as well. During the summer of 1854, a fierce and systematic cholera outbreak ravaged Soho: On one day alone, 70 people died in a single parish.

The cause was as plain as the nose on your face, according to the conventional wisdom of the day. The majority of physicians and scientists, along with many social reformers and concerned members of the clergy, firmly believed that disease spread through polluted fumes and toxic aromas, not peer-to-peer contact.

Although there were practically as many theories about the causes of cholera as there were cases of the disease, the dispute was largely between two camps: “the contagionists and the miasmatists. Either cholera was some kind of agent that passed from person to person, like the flu, or it somehow lingered in the ‘miasma’ of unsanitary spaces,” Johnson writes.

“All smell is disease,” Edwin Chadwick famously declared. London’s sanitation commissioner at the time of the outbreak, Chadwick was hapless if typically well-intentioned. Even Florence Nightingale, whom the author calls “the Victorian age’s most beloved and influential medical figure,” fell under the miasmatists’ sway. Johnson is sympathetic to their high-minded motives if somewhat merciless about the tragic ineffectiveness of their efforts.

The most vocal advocate of the contagion theory was a maverick named John Snow. A farmer’s son, Snow transcended humble origins to become a medical polymath: practicing physician, pioneer in the field of anesthesia, contentious contributor to medical journals, lecturer and researcher. Snow studied the Soho epidemic and eventually backtracked it to a water pump on Broad Street. But he wasn’t working alone. Henry Whitehead, a local curate with uncommon access to the neighborhood and unquestioned empathy for its residents, went house to house collecting data about residents’ daily habits and the incidence of the disease, information Snow used to shore up his controversial theory of waterborne contagion. Whitehead was a miasmatist when they met, though he wouldn’t remain one for long. “His religious values had brought him into close contact with the working poor,” Johnson writes of the urban minister, “but they had not blinded him to the enlightenments of science.”

Drawing on Whitehead’s data, Snow plotted a demographic death map. Put simply, this “ghost map” contrasted human behavior with geography, establishing that cholera deaths were clustered in houses within walking distance of a water source that proved contaminated. Snow and Whitehead’s efforts captured “a deeper truth by putting it on a map.” And for the first time, according to Johnson, a map became a triumph of information design and epidemiology as well as a rare documentation of “street level knowledge.”

“This is how the great intellectual breakthroughs usually happen,” he writes. “It is rarely the isolated genius having a eureka moment alone in the lab. Nor is it merely a question of building on precedent, as standing on the shoulders of giants, in Newton’s famous phrase. Great breakthroughs are closer to what happens in a flood plain: a dozen separate tributaries converge, and the rising waters lift the genius high enough ... [to] see around the conceptual obstructions of the age.”

However, the map “didn’t solve the mystery of the outbreak,” Johnson writes. “It didn’t lead to the pump handle’s removal and thus bring an end to the epidemic.” So, although “The Ghost Map” starts off with the brisk pacing and the suspense of a detective novel, it has no dramatic payoff. The story has a happy ending in that London got a sewage system -- the most advanced and elaborate in the world -- up and running by 1865. But this gradual (and realistic) resolution hardly disappoints.

In his previous book, “Emergence: The Connected Lives of Ants, Brains, Cities, and Software,” Johnson brilliantly posited ideas about the organization of systems from the bottom up. In “The Ghost Map,” he reveals just how those principles actually work in a messy, constantly decomposing real world. With this, his fifth nonfiction book, Johnson adds a new and welcome element -- old-fashioned storytelling flair, another form of street knowledge -- to his fractal, multi-faceted method of unraveling the scientific mysteries of everyday life. *