The Ghost Map: The Story of London’s Most Terrifying Epidemic—and How It Changed Science, Cities, and the Modern World

This chapter introduces Henry Whitehead, a Soho vicar at the time of the cholera epidemic. He is described as both gregarious and intellectual, and as prone to challenging received opinions. The reader is invited to imagine him doing his daily rounds about Golden Square—the crowded neighborhood where the epidemic began—and chatting with his parish. These rounds will later become a “death vigil” (53), as the epidemic sets in.

The chapter then traces the origins and the process of cholera, as well as its effects and the many misguided cures that existed at that time. While its cure in actuality is simple—to rehydrate a patient with cholera, which is a process of dehydration—most Victorian doctors did not attempt this method, instead relying on supposed cures such as castor oil or even opium. Adding to the confusion were the newspapers at the time, which displayed ads for various cures, and in which charlatans and opportunists as well as licensed doctors were able to advertise.

Johnson states that while cholera is an ancient disease, it did not arrive in England until the 18th century; before then, it was largely concentrated in Asia. It was the rise of densely populated cities, as well as these cities’ increasing connectivity through battles and shipping routes, that eventually brought cholera to England. Johnson makes the point that cholera is not an easy disease to contract, as it relies on the “eating of excrement”(40), an unnatural activity for humans. However, cities such as London—both populous and poorly sanitized—created natural breeding grounds for the Vibrio cholerae bacteria.

Moreover, V. cholerae took on a more virulent and fast-acting form once it made its way to London, a place where it could find many hosts side by side and therefore did not need to conserve itself: “There’s no incentive not to reproduce as violently as possible—and thus kill your host as quickly as possible—because there’s every likelihood that the evacuations from the current host will be swiftly routed into the intestinal tract of the new one” (44). Johnson describes the quickness with which bacteria reproduce and adapt, compared to the slowness with which humans and other “multicellular organisms” (42) do so. He makes the point that the planet is richer in bacteria than in any other organism: “[I]n reality it’s been one long Age of Bacteria since the days of the primordial soup. The rest of us are mere afterthoughts” (36).

The London cholera outbreak of 1854 killed those infected within 12 hours of infection. Johnson explains that people dying from cholera are mentally lucid right until the end. While making his rounds through Golden Square during the epidemic, Whitehead noted that some of the more elegant homes were affected by the disease, while some of the more squalid and less sanitary homes had been spared. This chapter also introduces a local doctor, John Rogers, and describes his own reactions to the devastation around him, as well as his conviction that the illness has sprung from poor sanitation.

This chapter introduces the physician John Snow, who was instrumental in discovering the cause of cholera. Snow is described as an intense, ambitious, and rigorous man, the son of a laborer who made his way to London. Along with his groundbreaking studies on cholera, Snow also helped to refine the use of anesthetics for surgery, at a time when ether was used either clumsily or not at all. Snow created a special application for ether that allowed its temperature, as well as its dosage, to be controlled. Despite his lack of an engaging bedside manner, he became an anesthesiologist to the wealthy and powerful, even anesthetizing Queen Victoria during the birth of her eighth son.

The chapter opens with Snow taking a sample from the Broad Street water pump, which the reader can discern from previous chapters to be the main source of infection in the Golden Square neighborhood. Snow has been examining the causes of cholera for several years, since a British cholera outbreak in 1848. At the time of his study, two popular theories prevailed about the causes of cholera. Cholera was believed to be either contagious or “miasmic”—that is, coming from the air and the atmosphere.

In his on-the-ground studies of the disease, Snow found that neither one of these explanations wholly made sense. He noted in particular a case where one man became ill with cholera after staying in the same hotel room where a previously ill man had stayed, while having had no contact with the first ill dweller himself. He also noted that while some poor households and unsanitary-seeming environments had been infected with cholera, others had been spared.

This chapter also returns to the perspective of Henry Whitehead, who is making his rounds through Golden Square at the same time that Snow is studying its outbreak. Whitehead notices some of the same incongruities that Snow does; for instance, he notices that wealthy households on the ground-level have been infected at least as frequently as have upper-level households. This empirical observation seems to contradict a widely held idea that cholera is a disease of the poor. At the end of the chapter, the author reveals that while Snow is studying a sample of water from the Broad Street pump, Whitehead has actually imbibed it, along with a pinch of brandy.

The quote from this chapter’s title comes from the Charles Dickens novel Bleak House. It refers specifically to a destitute child in the novel and more generally to the Victorian attitudes towards death. As Johnson states, mortality rates were much higher than modern-day, and dying in middle age was common even if one came from a wealthy background. He suggests that anxiety and paranoia—of the sort that many 21st century city dwellers experienced after 9/11—do not arise from experience with mass disasters, but rather from heightened expectations of safety. Conversely, populations who have witnessed many mass disasters—as the Victorian-era British did, including a number of cholera outbreaks—tend to have a more resigned and fatalistic view of death. 

At the same time, Johnson suggests that the Victorian attitude towards cities was a squeamish and paranoid one. Cities were seen as unsanitary, unnatural, and as having a sort of monstrous life of their own. This last view of cities, according to Johnson, had some partial intuitive logic to it. He points out how the existence of cities does not spring from individual will, but rather from “energy”(94) sources that feed on themselves and make mass populations possible. He uses the analogy of a garden, which grows on its own, as opposed to the construction of a building, which is always under human control. He identifies three particular energy sources that led to the rise of London: the Industrial Revolution, the merging of farming and capitalism, and the rise of railroads.

Johnson suggests that Victorian-era Londoners had not yet learned to see their city from a “birds-eye view,” that is, from a detached, high-up perspective. While they lived in a city, they were also intensely local. News traveled fast at the level of the postal service but was slow to be picked up by the city newspapers. Consequently, even trained scientists and statisticians were ill-equipped to deal with—and to find the causes for—an epidemic like cholera. A figure like John Snow was unusual, not only in his ability to look at cholera from both a lofty and an on-the-ground perspective and to utilize other disciplines besides his own, but because he was already well-established as an anesthesiologist and could easily have rested on his laurels:

Here we have a man who had reached the very pinnacle of Victorian medical practice […] who was nonetheless willing to spend every spare moment away from his practice knocking on hundreds of doors in some of London’s most dangerous neighborhoods, seeking out specifically those houses that had been attacked by the most dread disease of the age (108).

While Snow was beginning to suspect the means of transmission for cholera, at the time of the 1865 outbreak, he still did not know the precise cause of it. He was aided by the demographer William Farr, who, while himself a believer in the miasma theory of cholera transmission, was willing to indulge Snow in his investigations of how different water sources in the city corresponded to deaths from cholera. 

The title of this chapter refers to the once-popular belief that breathing in bad air could kill you. It is another way of referring to the miasma theory of cholera transmission: a theory that was held by Edwin Chadwick, among many other dynamic and influential figures. Chadwick was the president of the Board of Health, before Benjamin Hall replaced him.

Johnson suggests that this belief may in fact have contributed to the very cholera epidemics that it was trying to address. The amount of sewage in London was a cause for concern, but for the wrong reasons; in attempting to rid the city of its foul smell, officials decided on pumping water into the Thames River. The citizens then drunk this water, leading them to contract cholera. 

Johnson speculates that there were a number of unconscious reasons for the pervasiveness of the miasma theory. One reason was simply that the theory had intellectual tradition behind it. As Johnson states: “Just about every epidemic disease on record has been, at one point or another, attributed to poisoned miasma” (127). Johnson also notes how, particularly in Victorian times, the nose was more capable of perceiving illness than was the naked eye. Microscopes then were far less advanced than they are now; however, humans are evolutionarily equipped to sniff out microbes, even if they cannot see them. Miasma had the further advantage of being uncomplicated, as compared to the waterborne theory of cholera, and propelled by social prejudice—that is, the belief that the poor deserved to get sick.

Johnson observes that many of these justifications had some partial truth to them: “Methane and hydrogen sulfate were in fact poisons, after all; they just weren’t concentrated enough in the city air to cause real damage […] the poor did have higher rates of contagion than the well-to-do, but not because they were morally debauched “ (133). This was another reason the miasma theory, as a whole, lasted for as long as it did.

Because the miasma theory had the final result of foul water being dumped into the Thames, it ultimately served to highlight the true source of cholera epidemics. The chapter ends with Snow studying the Broad Street pump and deciding that he will need to establish not just the names of citizens who have died, but their trails through the city and their water drinking habits: “Snow was going to need footprints, too” (136).

As its title suggests, this chapter focuses on Snow steadily building on his theory of waterborne transmission. He comes to realize that if he is going to convince Benjamin Hall and other figures like him of the rightness of his theory, he is going to need some “deviations from the norm” (140). That is, he is going to need to find some cholera deaths that did not occur only around the immediate area of the Broad Street pump.

Johnson speculates that there were a number of reasons why Snow was not susceptible to the miasma theory of transmission. As a specialist in anesthesiology, he was in a position to observe what breathing in altered air could—and could not—accomplish. He noted that concentrated doses of ether or chloroform had generally predictable effects on people, regardless of who they were or where they came from. This likely disproved for him the theory that poor people were susceptible to cholera because of their bad characters and unhealthy lifestyles. He would also have noted that only concentrated doses of ether and chloroform put people to sleep, while he, as an administrator of the doses, was unaffected by them. This also likely made him suspicious of the theory that all bad air is unhealthy, whatever the dosage or intensity.

Snow also himself came from a humble background, and the demonizing of the poor that was inherent in the miasma theory may have rankled him. He also had a “methodological” approach to his work; that is, he started with his practice and built a theory from it, rather than the other way around: “Snow’s theory was like a ladder; each individual rung was impressive enough, but the power of it lay in ascending from bottom to top, from the membrane of the small intestine all the way up to the city itself” (148). Finally, as a doctor, he noted that the effects of cholera were in the intestines rather than the respiratory system, as would have been natural with a disease contracted from the air. 

This chapter also takes the perspective of Henry Whitehead, who is conducting a parallel investigation to Snow’s. While Whitehead is a man of God rather than a scientist, his approach is just as intensely local as Snow’s. His strength lies in his wide circle of acquaintances and also in his questioning and skeptical intellect. While he is a believer in the miasma theory, a vicar friend’s death from cholera leads him to question the idea that people who die from cholera have somehow brought it on themselves.  

Whitehead also notes the number of his acquaintances who have been cured by copious water drinking—from the same Broad Street pump that caused them to contract the disease in the first place. Johnson suggests that this apparent incongruity had its roots in bacteria, as does the disease itself. Over the course of that lethal week, the bacteria down in the well may no longer have been able to flourish, due to a lack of plankton and also due to the general clarity of the water. It is also possible that the bacteria itself was wiped out by another virus: “a viral phage that exploits V. cholerae for its own reproductive ends the way V. cholerae exploits the human small intestine” (152).  

At the height of the epidemic, Snow convinces the Board of Governors at the St. James parish to remove the handle from the Broad Street pump. They do so, but more out of desperation than conviction. Benjamin Hall, the president of the Board of Health, meanwhile instructs inspectors to examine the neighborhood in detail, but his detailed instructions continue to focus on smells rather than on water.

Whitehead initially tries to disprove Snow’s theory of waterborne transmission, but eventually comes to side with him. The two men find themselves on the same investigative team, one separate from the Board of Health and run by the vestry of St. James’s parish. Johnson argues that the vestry team’s lack of resources, as compared to that of the Board of Health, was a blessing in disguise, allowing them to come up with their own homegrown solutions rather than relying on received ideas.

Whitehead finally comes to accept Snow’s theory after he has interviewed Mrs. Lewis, the mother of baby Lewis, who was the “index case” (177)for the 1854 cholera outbreak—the cholera victim whose soiled diaper made its way into the neighborhood drinking water, leading to the general outbreak. Whitehead then directs a surveyor to examine the Broad Street well again, but this time to also look at the area around the well. The surveyor finds that the cesspool in front of the Lewis house, into which the diaper was dropped, was unclean and overflowing, and could easily have flowed into the well.

The vestry presents its findings to the Board of Health, which rejects the findings despite the careful reasoning and methodology behind them. Johnson suggests that the men on the Board of Health were not bad or prejudiced men but were simply “blinded by an idea” (184). Meanwhile, the epidemic forms a terrible full circle with the death of Mr. Lewis, the father of baby Lewis. While his death comes at the general dying out of the epidemic, Johnson speculates that had Snow not insisted on removing the Broad Street pump handle, the neighborhood could easily have been infected with a second strain of cholera: “And so Snow’s intervention did not just help bring the outbreak to a close. It also prevented a second attack” (188).