As an oppressive blast of late summer heat bore down on the estates of Hampstead, just north of London, Susannah Eley, a wealthy widow, was enjoying a visit from her niece. For almost the whole of August, England had baked under clear, motionless skies. What breeze there was carried in a blanket of thick, humid air laced with the fetid breath of London. As that last, cloudless day of the month wore on, the two ladies sipped from their water glasses in the sweltering heat.
They found nothing disagreeable in the taste of the water. It gave off no foul odor, nothing to suggest the presence of a disease-causing miasma. If either of them had looked closely, she might have seen a few fine white particles drifting in her glass, but in 1854 this was no cause for alarm. What possible harm could come from particles they could barely see? They had no reason to believe that death could come in such a small package.
The same heat that made the widow Eley and her niece uncomfortable made London’s inner city unbearable. Day after day the sun had slowly roasted the city’s noxious accumulation of human and animal waste. Each neighborhood had its own special topography of odor that rose and fell with the temperature. On a cool day, the terrain was challenging, but negotiable. In the heat of summer, the city’s residents struggled to find a path through these mountains of stench.
For Londoners who lived or worked among the dense jumble of residence and commerce between Golden Square and Soho Square on London’s East End this assault on the senses was unrelenting. At the street level, every manner of business and industry from breweries to slaughterhouses produced a full spectrum of offense. To this mixture stables, decrepit privies, and ancient cesspools added their own offerings, sending an unrelenting stink steadily up toward the homes of the working poor who crowded into tiers of one-room apartments above the street.
When the heat was less intense or the air less still, those who lived and worked on these dark and narrow streets might find a mouthful of untainted oxygen in the open expanse of Golden Square or on the few wide streets such as Marlborough or Broad, but they provided no such haven on that Thursday. As the heat grew on that last day of August, the vile reek of the privy outside the Newcastle-on-Tyne Pub at the corner of Cambridge and Broad laid siege to the four-story tenements next door. The residents crowded into the rooms above the boot tree maker on 40 Broad Street could either close their windows and swelter in the stultifying heat or open them and surrender to the putrid assault.
In one of those rooms, Susan Lewis, the wife of a policeman, anxiously prepared a bottle of rice meal and milk. In a world that did not understand sanitation, bottle-feeding often meant disease and even death for an infant, but Susan Lewis had no choice. An illness late in pregnancy had left her unable to breast-feed her infant daughter. The baby had now fallen seriously ill for the third time in her five short months of life. The attack of diarrhea, which had begun just four days earlier, had subsided, but it had left her weak with no appetite. Mrs. Lewis tried to stir her baby, offering the bottle and hoping she would eat. Instead the frail infant lay passively, taking nothing. Three years earlier Susan Lewis had lost her son before he reached his first birthday. Now the young mother feared the worst.
Two doors down workers at the Eley Brothers percussion cap factory replenished two large cisterns with water from the pump just outside their doors on Broad Street. In the heat the owners made sure to refresh their workers’ water supply regularly. They had recently noticed that the water tended to develop an offensive odor after sitting for more than two days, so they were particularly diligent in this task.
That morning workers at the factory had also filled a large bottle with water from the pump and packed it on a cart bound for the West End. For reasons lost to history, the Eley brothers’ mother preferred the water from the pump to that from wells far closer to her home. Perhaps she requested water from Broad Street out of some sort of affection for her late husband who had owned the factory until his death. Perhaps she simply preferred the taste of its water.
Whatever the reason Susannah Eley’s sons sent a cart laden with drinking water from the Broad Street Pump on its routine trip. Several times each week, the cart would make its way through the crowded streets of London, past the farms that surrounded the great city and out to Hampstead, a distance of four miles, to deliver a large bottle of water and, in the late summer of 1854, cholera.
As night fell on the lingering heat of that cloudless summer Thursday, the widow Eley and her niece drank the water from Broad Street, oblivious to the disaster that lay ahead. They could not have imagined that each of the minuscule particles suspended in the innocence of drinking water contained millions of deadly comma-shaped bacteria, the telltale form of Vibrio cholerae. That night the strong acids in the widow’s stomach destroyed almost all these microscopic invaders and might have saved her had they not been so numerous. The massive dose in each glass of water ensured that some of the bacteria would find their way through her stomach to the haven of her small intestine.
The hydrochloric acid that had dissolved her evening meal packed the corrosive power of battery acid. In addition to destroying most of the bacteria, it would have eaten through the walls of her stomach were it not for the thick protective slime secreted from its lining. This coating worked well for the crude operations of the stomach. The small intestine had a far more intricate task. It would need to break down the nutrients in the slurry of food passing through its thirty-foot length and transport them molecule by molecule into the widow’s bloodstream. Any protective layer would make this impossible. Instead specialized cells released just enough bicarbonate to neutralize the acidic mixture flowing from her stomach to protect the delicate lining of her small intestine. That night the bicarbonate also granted a reprieve to the cholera.
As the night wore on, the few surviving bacteria had already begun to reproduce inside her. When she awoke their numbers were still so small that Susannah Eley had no notion of the danger at hand. Back on Broad Street, however, disaster had already begun to rear its head.
Homes throughout the neighborhood had spent a night in sheer terror as family members plummeted into the abyss of cholera. On the morning of Friday, September 1, as the people of Soho stepped outside, they found that a cooling breeze had arrived from the northeast, but something far worse than a heat wave had arrived in the dark of night. Word of the horror buzzed through the neighborhood. Almost everyone, it seemed, knew someone who was dying.
No one understood the scope of the disaster better than Reverend Henry Whitehead, the priest of St. Luke’s Church, which stood just one block from Broad Street. Throughout the previous evening and into the night he had walked the streets of his parish in long, flowing robes ministering to the afflicted and their families. For many the appearance of his broad, friendly face gave them a moment of reassurance in an otherwise desperate night. When he finally made his way home through the dense mix of mist and coal smoke to the small apartment that he shared with his brother, he sensed he was facing a devil unlike any he had encountered in his twenty-nine years. He would spend much of the next day delivering last rites to the dying.
Word of the emerging tragedy had yet to reach the affluent district just across Regent Street where John Snow had immersed himself in a study of the London water supply. His office was filled with maps, death records, and the data he had assembled over the preceding year on the relationship between water supply and cholera deaths in an area south of the Thames. He had recently cut back on his clinical work so he could devote even more time to his experimentum crucis. So as the morning of Friday, September 1, arrived, he was simply relieved that the heat wave had broken.
After six years of struggling to convince the medical establishment that drinking water could spread cholera, John Snow felt he was finally closing in on the proof that might muffle his critics. The ground itself would need to shake to divert his attention from the task at hand. He would soon discover that an epidemiological earthquake like no other had its epicenter on the north side of the Thames, just a short walk from his front step.
But as the sun rose on that Friday morning, John Snow had no notion of the horrifying turn of events so close to the desk where he sat piecing together the story of the London water supply. He could not see the first black, windowless carriage as it appeared from behind the curtain of fog that the cool air had draped across Broad Street. He could not hear the horses protest as its driver, also dressed in black, pulled at their reins, bringing the carriage to a stop in front of a four-story building. Two men climbed down and entered the front door with a stretcher. They climbed to an apartment marked by a row of shuttered windows. Minutes later they emerged carrying a draped, lifeless figure. Before they had finished loading the corpse into the back of their carriage, the sound of hoofbeats and steel-rimmed wheels signaled the arrival of another crew with the same grim mission.
Over the course of that day, a fleet of hearses rolled steadily through the district. Again and again these faceless wagons came to collect their tragic cargo. More than sixty people living in the area around Broad Street died on that Friday. As each hearse arrived, neighbors watched, quietly registering the address of the deceased and wondering where the next would stop.
But the worst was yet to come. Throughout the day the blue death roamed the district, visiting one home after another, selecting its next victims with an apparent randomness that was both cruel and terrifying. As word spread of each new case, fear grew palpable. Those who rented furnished rooms and did not have a friend or relative in need of their care packed up their belongings to seek refuge elsewhere. Before Friday found its end, 143 more people were fatally ill. Still the ravages of cholera were just beginning.
Of those to whom cholera had laid siege on that Friday, all but two lived within a few blocks of the Broad Street pump. To reach these last victims, however, the disease had traveled to the comfortable homes of Hampstead. There, far from her deceased husband’s Broad Street factory, Susannah Eley began to feel a vague discomfort.
The bacteria in her small intestine had spent much of the day doubling and redoubling. As the Vibrio cholerae multiplied, they busily manufactured a deadly poison. The toxin targeted the switches in the lining of the intestine that controlled the flow of bicarbonate, jamming them into the “on” position. Susannah Eley could not notice the initial trickle of fluid that seeped into her gut. But as the numbers of bacteria grew, vast quantities of bicarbonate began to flow into the widow’s small intestine.
By hacking into the signal pathways of her digestive system, the bacteria created a surging torrent of acid-neutral fluid, full of nutrients in which they could grow and reproduce. What had been the machinery of digestion became a factory for the production of billions upon billions of pathogens that rode the flood of bicarbonate out into the world in search of other victims. It was not the bacteria, but the river they created that would kill her.
As the first day of September tumbled into darkness, cholera tightened its grip on Broad Street. Early on Saturday the parade of hearses began again. Throughout the day they arrived with increasing frequency, each one departing laden with its grim payload. Late in the afternoon, one arrived at 40 Broad Street. It carried off a tiny corpse and left Susan Lewis consumed with grief over the death of her second child.
Even in a city that had learned to live with cholera, a disaster of this intensity attracted notice. By Sunday, September 3, word had spread through London. When the news reached the office on Sackville Street where John Snow was untangling London’s complex network of water supplies, it found the one person who could understand what had happened.
In the mind of Snow, only drinking water could cause such a sudden explosion of cholera. He also knew that two water companies supplied piped water to the area affected by the outbreak; the Grand Junction Company supplied the western portion near Golden Square and the New River Company supplied the eastern portion near Soho Square. Not only did both companies have relatively clean sources of water, they drew from entirely different rivers. The simultaneous contamination of both sources defied probability. More important, Snow knew that anything involving these companies would have affected a much larger area than the highly localized disaster at hand.
As he gathered his hat and stepped out into the fading heat of summer, John Snow felt certain that the “morbid matter” that caused cholera had made its way from a victim of the disease and into some single, common source of water. He reasoned that a contaminated public well must have given rise to the outbreak.
As usual the Sunday evening traffic was light as he made his way across Regent Street. Not only did John Snow understand cholera, he knew the Broad Street neighborhood as well as anyone. His first two residences in London were just a few blocks east of Broad Street and now he lived in a comfortable home a few blocks to its west. There was only one pump that could have caused the pattern of death that his medical friends had described to him and he was walking straight toward it.
His footsteps echoed across the cobblestones as he walked through Golden Square and turned onto Silver Street. Even for a Sunday, this gritty, commercial neighborhood was unusually quiet and empty. He continued on past the National School and onto a wide street that was just over four blocks long. Passing beneath the watchful eye of the stone lion perched above the Lion Brewery, he could see the yellow pestilence flags that hung limply from the lampposts. Throughout the deserted street, the shuttered windows of mourning marked the homes of those who had already died. Halfway down the street, he stopped. He carefully removed a small bottle from his pocket, lifted the handle of the Broad Street pump, and held it under the spout.
Even Snow had to rely primarily on his senses to test the water. He examined the contents of the bottle looking for any hint of contamination. He saw and smelled nothing to suggest the presence of organic matter in the water. His years of scientific training had taught him the value of skepticism, particularly in the evaluation of one’s own, best ideas. He left unconvinced that he had found the source of the outbreak.
He continued on through the neighborhood, determined to find the water pump that cholera had used to launch its attack. At the Warwick Street pump, he saw small white, flocculent particles in the water. He found similar impurities in the water at Bridle Lane. The dirtiest water came from the pump on Marlborough Street, but passersby informed him that this was well known in the area. Most people, he learned, preferred to gather their water from the pump on Broad Street.
When John Snow returned home that night, he remained convinced that a water pump had caused the ongoing disaster. The pump on Broad Street remained the prime suspect. He was equally certain that finding the exact cause and demonstrating its role to a deeply skeptical audience would require far more work. No one in London shared John Snow’s concern about the water from the Broad Street pump. Those who remained in the area continued to collect its water, just as they always had.
As the last hour of that tragic weekend slipped away, Reverend Henry Whitehead sat down to rest. This had been a weekend like no other in his life. All his waking hours had been spent as an observer at death’s door trying to bring some measure of comfort to the dying and the desperate. Drained of his physical, emotional, and spiritual energy, he sought to soothe his own soul with a glass of brandy. He diluted it with water he had drawn from the Broad Street pump.
John Snow’s continued inquiries led him with increasing certainty to a single explanation for the pattern he saw in the mounting cholera deaths. On Monday, after providing chloroform for a tooth extraction, he returned to the Broad Street pump. Even if he could not see it, smell it, or taste it, cholera’s cause must be hiding in the well. This time, he took several samples to test.
Using one of the few reliable tests available to him, Snow added a few grains of silver nitrate to the sample. He shook it and the water grew cloudy with crystals of silver chloride. The fine grains sank in the water and accumulated on the bottom of the flask. Even before he weighed them, experience told Snow that the amount of chloride in the water was high. Chloride marked the presence of sodium chloride or salt. Since pure well water should contain very little salt, something must be contaminating the well.
Snow took another sample to Dr. Arthur Hill Hassall, one of London’s most eminent microscopists and author of an authoritative book on the minuscule inhabitants of water. Hassall reported finding organic matter and oval “animalcules” in the sample. These may well have included Vibrio cholerae, but at the time Snow had no way of knowing this. Instead he only took this to be evidence of organic contamination, all the evidence he needed to continue to focus on the Broad Street pump. Somewhere in those contaminants, he reasoned, cholera’s demon was hiding.
The members of the medical establishment would not see the evidence the same way. After all hadn’t Snow’s own examination shown that other pumps were also contaminated, perhaps more contaminated than the one at Broad Street? Snow’s theory required them to believe not only that undetected contaminants could kill, but also that this would happen only when a special variety of these invisible killers was present. At a time when microbiology did not exist as a science, he would need the tools of epidemiology to make his case. But the tools he needed did not exist, would not exist, until John Snow invented them.
On Tuesday, at his first opportunity, he set out across Piccadilly Circus and then through the maze of London’s streets until he reached the Strand, a grand promenade in front of the imposing buildings that lined the north bank of the Thames. There he entered Somerset House, a vast stone edifice that was home to the government’s leading societies of science and art. Deep in its marbled bowels, he made his way to the Office of the General Registrar, where William Farr and his employees would be assembling the official record of cholera deaths for the preceding week.
That same morning the British Government had taken official notice of the outbreak. Sir Benjamin Hall, president of the General Board of Health, toured the scene of the disaster. Three-quarters of the area’s residents had fled. Those that remained and were able clustered around Dr. Hall in the hope that the attention of the authorities would bring them some relief. Tall and handsome, Hall’s striking figure earned him a nickname he would one day share with the largest clock in London, Big Ben. On this grim day, there was no missing him and his entourage as they walked the streets around the Broad Street pump. As they moved the hearses were busy again. On that day alone, forty-five people would die.
The next day as he monitored his anesthetized patients, John Snow’s mind buzzed with thoughts of the unfolding outbreak. The general registrar had given him a list of all cholera deaths in London for the period from Thursday, August 31, through Saturday, September 2, the first weekend of the outbreak. Of the eighty-nine people on the list all but six had died within a few blocks of Broad Street.
As soon as he finished his clinical work, he returned to Broad Street and began to work his way down the list. At each household where someone had died of cholera, he would express his condolences and in a quiet, husky voice, he would inquire as to the habits of the deceased. Eighty-three times, he asked if cholera’s victim had used the water from the Broad Street pump.
Within twenty-four hours, he had eighty-three answers and a clear pattern had emerged. Seventy-three of the victims had lived closer to the Broad Street pump than any other and every one of them routinely drank its water. Of the ten who lived closer to other pumps, five had preferred the water from the Broad Street pump and always requested it and three others were children who went to school on Broad Street and routinely drank from the pump. Out of all the cholera deaths in the area, only two of the deceased drew their water from other wells.
On the following Thursday, one week after the outbreak began, the Board of Guardians of St. James Parish assembled in an emergency meeting. Hundreds had already died in their small parish and the death toll continued to mount. By virtue of England’s poor law, the board was charged with overseeing care for the indigent in an area of northeast London that included Broad Street and Golden Square. As they met to discuss the crisis in their midst, a stranger arrived at the Vestry Hall requesting an audience.
A balding man with intense, deep-set eyes entered the room and introduced himself as Dr. John Snow. He had spoken in the building before at the meetings of the Westminster Medical Society, but never had his message been so urgent. Standing in the elegant boardroom with floor to ceiling windows overlooking Piccadilly, Snow laid out his indictment of the pump and implored the board to close it. The board members listened as he described his investigation of the eighty-three cholera deaths and his indictment of the Broad Street pump. They doubted that drinking water could have caused such an epidemic, but ready to try anything, they relented. After all, anyone who could had fled in the face of the outbreak. When those still in the neighborhood came for water the next day, they found that the Broad Street pump had no handle. For the first time in history, a governing authority had taken action intended to halt an outbreak of waterborne disease.
In the fields of epidemiology and public health, removing the pump handle has become the stuff of legend, but even Snow himself was not convinced that doing so had saved any lives. Even though thirty-two people died of cholera on that Thursday, the outbreak was in decline and might well have abated without the closure of the pump.
Ultimately 623 people in this small neighborhood died of cholera in just over a week. Hundreds if not thousands more had contracted the disease, but managed to escape with their lives. London had not seen an outbreak of such focused ferocity since the darkest days of the bubonic plague. Most of the survivors had left the area, turning the normally busy commercial district into a ghost town.
Some had nowhere to go. In the wake of the disaster, a struggling intellectual by the name of Karl Marx sat in a sparsely furnished Soho apartment and recorded his impressions in a letter to Friedrich Engels.
[T]he total absence of money is the more horrible—quite apart from the fact that family wants do not cease—as Soho is a choice district for cholera, the MOB is dropping dead right and left (e.g. an average of 3 per house in Broad Street) and victuals are the best defense against the beastly thing.
As cholera burned itself out, tragedy gave way to mystery. The outbreak had ended, but the investigation of its cause was just beginning.
By the middle of September, the disaster had spawned no fewer than four studies, each relying on its own particular brand of epidemiology and sending investigators scurrying through the neighborhood in search of cholera’s cause. The most prominent among these came from Benjamin Hall and the General Board of Health, which had charged three of its members with investigating a long list of concerns including atmospheric conditions, ventilation, the presence of nuisances and noxious trades, bad smells, privies and cesspools, the state of basements, and the quantity and quality of the water supply in the affected area. The fact that the water supply was included at all may have been a begrudging nod to the theories of Dr. Snow, but its place at the bottom of the list and the nature of the remainder of their tasks leaves little doubt that they were on a mission to find the miasma that had unleashed the epidemic.
As the Board of Health team sniffed its way through the neighborhood, the worst stink of summer had already diminished. Instead the acrid odor of lime overwhelmed the district. As part of a daily cleansing ritual, the Board of Guardians had ordered workers to coat the streets where cholera had struck with the heavy white powder. The blackened figures of mourning survivors cast somber shadows on what appeared at first glance to be a late summer snowfall. It seemed as if cholera had drained the color from Broad Street. Day after day John Snow made his way around snow white puddles to the homes of the mourners and asked about drinking water.
Snow had been a regular visitor to the Office of the General Registrar since the outbreak began and his list of names had grown steadily as the death toll continued to rise. In addition he had recognized that the official tally was missing many deaths of people who had not died in their homes. Those who lived solitary lives clinging to the lowest rungs of society’s ladder found their only care at Middlesex Hospital, five blocks south of Broad Street. Years later Florence Nightingale would recall her experience as a young nurse there during the first weekend of the outbreak. For three days she had worked without sleep as a steady stream of dying prostitutes and their fellow denizens of the street arrived with the icy hand of cholera around their throats. For days she could do nothing more than comfort them and watch them die.
Others were lost to the system because they had suffered the fatal misfortune of consuming the water from the pump before leaving to die elsewhere. At a chance meeting with Dr. Charles Frasier, the only physician on the team sent by the General Board of Health, Snow learned of two such cases. The first involved a man from Brighton who had come to care for his brother, but arrived to find he had died. The man saw no reason to linger in the presence of cholera, but he was hungry from his journey and had a long trip home. His sister-in-law prepared him a quick meal of rump steak. He washed it down with a tumbler of brandy and water from the Broad Street pump. After twenty minutes he was back on the road to Brighton carrying a lethal dose of cholera.
The second case involved the mother of three sons, all of whom worked on Broad Street. For Snow it was the exception that proved the rule. He had already spent considerable time talking to the brothers as they ran a business where sixteen workers had died of cholera. The business was Eley Brothers’ Percussion Cap Factory and one of the three brothers told him of the regular deliveries of water to their now deceased mother. After following the path of the cart out to the home of Susannah Eley in Hampstead, Snow learned that the widow’s ill-fated niece had died on the same day as her aunt, miles away in Islington. Cholera was a stranger to both of these districts. The only thing that connected the isolated and simultaneous cases was a bottle of water from Broad Street.
Snow’s conclusions may seem painfully obvious to us, but we have the advantage of knowing he was right. The rest of London was looking elsewhere for the answers. In the words of Dr. Edwin Lankester, a prominent physician and member of the Board of Guardians who had listened to Snow’s plea to remove the pump handle, “not a member of his own profession, not an individual in the parish believed that Snow was right.”
As the neighborhood sought to regain its equilibrium, many of the survivors developed their own theory as to what had happened. Almost two hundred years earlier, William Earl of Craven had lived in an estate on Drury Lane, not far from what would become Broad Street. As the black plague ravaged the city, he had built several dozen pest houses in an area that included the west end of the future Broad Street. Victims of the plague, instant pariahs in a world that fled at the sight of their sore-ridden bodies, would come to this pest field to find refuge and in most cases to die. Their corpses accumulated in vast pits near the field. Many survivors of the cholera outbreak became convinced that recent excavations for new sewer lines had disturbed the pest pits and unleashed the remnants of this long-buried evil on the neighborhood.
This belief gained such credibility in the neighborhood that Karl Marx wrote in another letter to Friedrich Engels,
The cholera epidemic, now much abated, is said to have been particularly severe in our district because the sewers made in June, July, and August were driven through the pits where those who died of the plague in 1668…were buried.
Spurred on in part by this concern, the Commission of the Sewers sent an engineer by the name of Edmund Cooper to investigate the condition of the sewers in the neighborhood. The commission however had no intention of accepting blame for this disaster. His report, issued after just two weeks of peering down gully holes, concluded that bad smells had indeed caused the outbreak, but went on to state that the smells had come from within the houses. The sewers, he affirmed, were in good shape and could not have played a role.
One evening late in September, Reverend Henry Whitehead paid one of his frequent visits to the oil shop on Broad Street. Outside the shop a large barrel labeled CHLORIDE OF LIME in bold block letters offered its contents to passersby. A few minutes later he left carrying a large tin of kerosene. He would be staying up far into the night, working by the warm light of a flickering lamp to put the finishing touches on his own study of the outbreak that had struck at the heart of his congregation. Within a few weeks, he had issued his report, The Cholera in Berwick Street. It made no mention of the Broad Street pump.
As a priest of St. James Parish, he knew of Snow’s theory about the pump, but was convinced that Snow was wrong. After all Whitehead had drunk from the pump himself with no apparent ill effects. (He could not have known that brandy at high concentrations could protect him from contaminated water. We can suspect that, in the midst of the outbreak, he did not add much water to his brandy.) Furthermore he had been at the homes of three cholera victims who had consumed quart after quart of water from the pump during their illness and had recovered fully from the deadly disease. Whitehead boasted to a medical friend that he understood the dynamics of the outbreak far better than Snow and could prove the irrelevance of the pump if given the time. He would soon be given the opportunity to do just that.
As the fall wore on, the community had no real answers as to the cause of the outbreak. The General Board of Health had finished gathering data, but there was no sign of a report. If, as expected, the report blamed uncontrolled odors within the neighborhood, it would represent an implicit indictment of the Board of Guardians and by extension the Vestry of St. James, since they were responsible for the public health of the district. On November 23, 1854, almost three months after the start of the outbreak, the vestry commissioned its own study.
Epidemiology is deceptively difficult. The committee assembled by the Board of Guardians discovered this after a questionnaire sent to every home in the neighborhood produced no useful information. The board then summoned Dr. Snow for his input, as he was already a respected epidemiologist regardless of his views on water and cholera. After a meeting on December 12, the Board of Guardians added eight new members to the committee. The additions included Dr. Snow and the Reverend Henry Whitehead. This would be the beginning of a remarkable relationship.
Whitehead made no secret of his belief that Snow was wrong and his determination to prove him so. He routinely worked until 4 A.M. assembling data. He visited every home on Broad Street, many of them several times, to ask in detail about the outbreak. He was convinced that he had identified a key flaw in Snow’s work and in many ways he had.
Snow had looked almost exclusively at those who had died from cholera and asked about their exposure to water from the pump. However he did not investigate those people who did not die. What if everyone in the area drank from the Broad Street pump? In that case the fact that most of the victims had used the pump would mean nothing more than that they had resided in the neighborhood.
Despite their fundamental disagreement, Snow and Whitehead developed a growing respect for one another as the work of the committee progressed. They both worked tirelessly on their study of cholera and were both scrupulously objective in their review of the data. In January, when Snow published a revised and substantially expanded version of his monograph, On the Mode of Communication of Cholera, he gave a copy to Whitehead. The most prominent addition to the new version was an exhaustive account of his study of cholera rates among the London water companies. Snow viewed this as his masterwork, the definitive proof his critics had been demanding. He had also included a substantial section on his study of the Broad Street pump.
Upon receiving the slender volume, Whitehead read the section on the Broad Street outbreak with great interest. He pored over it, looking for two critical numbers, the rate of cholera deaths among those around Broad Street who drank from the pump and the rate of cholera deaths among those who did not drink from the pump. If the rates were similar, as Whitehead expected, it would confirm his belief that the pump water had not caused the outbreak. Snow had not included these key numbers, so Whitehead decided to generate them himself.
Over the next months, Whitehead worked feverishly to amass the data needed to calculate the death rates. He focused exclusively on Broad Street since this would leave no ambiguity about the proximity of the pump. Well-liked and highly respected among local residents, he visited homes again and again until he was certain as to their source of drinking water during the days surrounding the outbreak.
On one such visit, he sat with a man and woman whose adult daughter had died of cholera. The husband sat quietly as his wife told Whitehead that they all drank exclusively from their cistern, which stored piped water. Whitehead asked specifically what they drank on September 1, the day before their daughter died. She remembered her husband and daughter drinking gin and water that evening and assured Whitehead that the water was from the cistern. Unlike any of the others investigating the outbreak, Whitehead knew the people he interviewed. Knowing that the husband was almost deaf, he asked in a loud voice if his wife’s recollections were accurate. No, the old man informed the priest, he and his daughter had used water from the Broad Street pump on that evening. He boiled his water, preferring a hot drink. His daughter drank it cold. Twenty-four hours later, she was dead.
That spring the General Board of Health finally issued their report on the outbreak. They put little stock in Snow’s contention that “the real cause of whatever was peculiar in the case lay in the general use of one particular well, situate [sic] at Broad Street in the middle of the district, and having (it was imagined) its waters contaminated by the rice-water evacuations of cholera patients. After careful inquiry,” the report concluded, “we see no reason to adopt this belief.” Instead they rambled on for more than three hundred pages in a convoluted effort to explain how unique atmospheric conditions conspired with the inadequate sanitation in the district to ignite the epidemic.
By then however Whitehead’s late nights parsing data were leading him to an entirely different conclusion. After interviewing more than four hundred residents of Broad Street, he determined that those who drank from the Broad Street pump in the days surrounding the outbreak were nine times more likely to have died from cholera than those who used water from other sources. Epidemiologists now refer to these comparison rates in exposed and unexposed groups as a relative risk, but Whitehead had no such term. He only knew that his endless hours of work to establish the innocence of the pump had done the opposite. He had developed compelling evidence that Snow was right.
Still no one could find the source of the contamination that had caused the cholera. Where was the index case, the case that preceded all others? Then on March 27, 1855, long after others had closed their casebooks on the outbreak, Henry Whitehead was scrutinizing death records when something caught his eye. An infant had died of diarrhea on September 2 after an illness of four days. That would put the onset of illness at August 29, two days before the start of the outbreak, roughly the time it takes to contract cholera. The line that stopped Whitehead in his tracks was the address, 40 Broad Street, right in front of the pump.
He rushed off to speak to the mother of the baby. He found the grieving widow dressed in black in the shuttered darkness of her room on 40 Broad Street. In addition to losing her child to diarrhea, she had lost her husband to cholera. Her name was Susan Lewis. She described her desperation on August 29, as she struggled to attend to her daughter who suffered from profuse diarrhea. She had worked constantly to keep her clean, returning time and again to the basement where she washed the soiled diapers. For two days she had poured bucket after bucket of wash water into the sink, which drained into the building’s decaying cesspool.
Next Whitehead consulted Dr. Rogers, the physician who had cared for the dying baby. Rogers felt that the symptoms were not at all typical for cholera and believed that this was some other ailment. Undeterred Whitehead convinced the Cholera Inquiry Committee of St. James to commission the excavation of both the well and the cesspool for 40 Broad Street. When the subsurface was laid naked, it showed a clear muddy trail. Each bucket of water from the dying infant had sent a plume of contaminated water into the soil around the cesspool. From there it had seeped across three feet of saturated soil, and down into the well for the Broad Street pump.
In mid-nineteenth-century London, one in eight children never reached their fifth birthday. The plight of this infant would have received little notice but for the chain of events touched off by the simple act of a mother caring for her dying baby. Henry Whitehead had traced the river of cholera to its headwaters.
In his efforts to discredit Snow, Henry Whitehead had proved himself to be the doctor’s most apt and disciplined student. The two had worked closely together for months and a lasting friendship founded on mutual respect emerged. Whitehead held Snow in such high esteem that twenty years later a portrait of his friend was still hanging on his wall, a portrait that, he said, “ever serves to remind me that in any profession the highest order of work is achieved not by fussy demand for ‘something to be done,’ but by patient study of the eternal laws.”
On one day during that long winter of 1854, as the two men worked together to understand the “eternal laws” that governed the spread of cholera, Snow turned to Whitehead and said, “You and I may not live to see the day, and my name may be forgotten when it comes, but the time will arrive when great outbreaks of cholera will be things of the past; and it is the knowledge of the way in which the disease is propagated which will cause them to disappear.”