WHILE VISITING LONDON recently, I took my eleven-year-old daughter to a narrow lane once known as Broad Street and now called Broadwick. Doctors and public health mavens of all stripes make pilgrimages to this corner of Soho in honor of John Snow, the man credited with inventing the modern field of epidemiology. It was Snow who toppled the long-standing medical opinion that foul-smelling vapors, or miasmas, emanating from ubiquitous mounds of rotting garbage and feces caused cholera, the most dreaded disease of the nineteenth century. And since this remarkable physician applied a decidedly cartographical approach to solving a centuries-old quandary, his work serves as the centerpiece of Tom Koch’s elegantly written and richly illustrated book.
Snow’s fascination with cholera began when he encountered it professionally in the seaport town of Sunderland, near Newcastle, in 1831. Twenty-three years later, he tracked down the sources of London’s great cholera epidemic of 1854 by meticulously surveying every case, even to the point of checking each home’s water bills. The good doctor discovered that Londoners who drew their water from the Southwark and Vauxhall Water Company, which came from the fecal-contaminated Thames River, contracted cholera nine times more often than those whose water was supplied by the Lambeth Company, which originated from an upstream (and cleaner) source.
Broad Street looms so large in the imaginations of infectious disease experts because of Snow’s subsequent study of cholera’s effect on that avenue. While drawing up detailed maps of the neighborhood, he noticed that some five hundred fatal cases of cholera—which occurred over ten days—arose not more than a hundred yards from a widely used water well. Upon determining that a sewer pipe passed a few feet from the well, Snow convinced the parish councilors to remove the well’s pump handle, thus making it inoperable and the tainted water drawn from it unavailable. And lo and behold, the cholera cases in the neighborhood fell dramatically.
Although Snow hypothesized that a waterborne “poison” capable of self-reproduction was in the excreta and vomitus of the cholera patients and, ultimately, the water supply, Victorian medicine was nowhere close to our modern understanding of cholera as the result of consuming water or food teeming with a comma-shaped bacillus called Vibrio cholerae. Back in 1854, the mere suggestion that tiny microbes were capable of wreaking such havoc would have been laughable to the overwhelming majority of physicians practicing on both sides of the Atlantic Ocean.
No, that discovery would not occur until a few decades later thanks to another man named Koch—Robert Koch, the eminent bacteriologist and co-founder (along with Louis Pasteur and Joseph Lister) of the germ theory of disease. In 1876, Robert Koch conducted experiments demonstrating the bacterial cause of anthrax, a major disease among shepherds and woolgatherers given that sheep enjoy rolling about the pasture and are frequently infected with the spores causing the clinical illness. In 1882, he astonished the world again by announcing he had discovered the cause of tuberculosis, a feisty microorganism called Mycobacterium tuberculosis. In the following year, a severe cholera epidemic struck Calcutta and Bombay before moving westward to Egypt. Robert Koch and his intrepid assistants travelled to Alexandria where they conducted numerous autopsies, cultured every microbe they found, and demonstrated that the gastrointestinal tracts of those who succumbed to cholera were riddled with Vibrio cholerae. It was a Q.E.D. moment of gargantuan proportions.
Tom Koch, a medical geographer, applies this dramatic chapter in the history of medicine to demonstrate how maps were critical to epidemiology long before the germ theory of disease was ever uttered, let alone proven. Maps, he cogently explains, “make arguments about disease, their pattern of incidence, and their method of diffusion. They are workbenches on which we craft our theories about the things that cause health to fail, imaging data collected in this or that disease outbreak. They are not, as some might argue, either mere representations of the world or simple illustrations of work completed in other media.”
During the great plague epidemics of the Middle Ages, for example, maps played a key role in the public health responses of the day including the quarantine. With the realization that the path of the Black Plague pandemic of 1347-1348 was identical to the human network of trade, the ruling government of Venice developed a way to impede that spread by halting the movement of goods and people into its port for a period of forty days, hence quarantine or quarantenaria. During the seventeenth century, cordon sanitaires were developed across Europe thanks to the practice of disease mapping. Borders of armed guards prevented potentially plague-ridden travelers from entering a specific area and sequestered regions were delineated to house those who were stricken with the disease. And while such an approach may sound terribly antiquated, if not outright cruel, modified versions of these “non-pharmaceutical interventions,” as the U.S. Centers for Disease Control and Prevention now terms them, not only played a major role in attenuating the terrible influenza pandemic of 1918, they also helped save lives during the more recent H1N1 flu pandemic in 2009.
Koch brilliantly demonstrates the temporal and intellectual links between infectious disease mapping and the doctor’s quest to map the human body, ranging from the flawed work of the second century physician Galen of Pergamon to the magisterial anatomical text, De Humani Corporis Fabrica, by Andreas Vesalius (1543). Koch describes Vesalius’s scientific masterpiece as a book that presents “the body simultaneously as a landscape within whose components disease prospered or health resided, and as a landscape within the landscape of the world shared by all.” Those familiar with Vesalius’s famed “muscle men” will recall that behind each figure are artfully rendered landscapes of the Italian countryside; if placed page along page in one long line, as opposed to bound sequentially in book form, those landscapes make up one long vista. To this day, anatomy textbooks are referred to as “atlases.” Such a quaint name is actually a fitting tribute to mapmaking. Just as a traditional atlas informs the reader of the terrain, hills, valleys, bodies of water, and other topological aspects of a particular place in the physical world, the anatomy atlas informs the doctor of the key landmarks of the human body. It explains, with pictures and diagrams, how one structure or organ relates to another and at what critical points a surgeon should enter, manipulate, remove or revise a particular body part in search of a cure.
Elsewhere in the book, Koch discusses the yellow fever epidemics that stalked eighteenth-century America, typhoid fever epidemics of the late nineteenth and early twentieth centuries, and the polio scares of the first half of the twentieth century. More cursorily covered are the recent H1N1 flu epidemic of 2009 and the ongoing struggle to contain HIV/AIDS. And still less well examined is the question of how modern bacteriology and virology enlisted and usurped disease mapping. While Tom Koch presents a short closing chapter on how disease mapping has been employed in tracking clusters of cancer cases, he does not fully explore how modern-day physicians are actively mapping a cornucopia of maladies, including the incidence of multiple sclerosis in relation to climate and longitude, increased rates of childhood asthma, especially among those youngsters living in inner cities and near air polluting factories, and the virtual social network maps health researchers have constructed to study the rise of obesity and other behaviorally-based health issues.
But such quibbles are the essentially the stuff for a book on the medical geography of our own time. Disease Maps is a sumptuous exploration of epidemics of the distant past and the geographical analyses that explained and transformed them. Well-written and replete with detailed, archival maps of episodes of bubonic plague, cholera, and yellow fever, it will delight and inform those who are fascinated by epidemics or those who are simply curious about how doctors of the past attempted to understand and to combat once seemingly cataclysmic events.
Howard Markel, the author of An Anatomy of Addiction, is the George E. Wantz Distinguished Professor of the History of Medicine at the University of Michigan.