Take one part Dr. Gregory House, add a bit of Sherlock Holmes and a pinch of modern forensic science, and you have Dr. John Snow, a man who solved one of the largest mass killings in Victorian London.

The culprit: cholera. Ever since it first appeared in Britain in 1831, cholera periodically ravaged the cities, leaving thousands dead in its wake. In 1848-9, over 14,000 Londoners died; in 1853-4, another 10,000 succumbed. That the disease was somehow related to the deplorable conditions of British cities at the time was clear, but the means of transmission was believed by all authoritative men of medicine to be via “miasma”. Miasma was thought to be a sort of poisonous vapor or mist originating from decomposing matter, called miasmata. (Similarly, the word “malaria” comes from the Italian meaning “bad air”.) To prevent outbreaks, it was thought to be a simple matter of removing the miasmata. That many of London’s cholera outbreaks occurred along the banks of the Thames, the stinking fetid pool that was the depository of much of the capital’s sewage, only served as proof of the theory’s validity.

Death rowing on a putrid Thames surrounded by miasma.

Of course, the areas along the Thames were also the poorest and most tightly packed quarters of London with the most inadequate sanitation facilities. Beneath many houses was a cistern, usually filled to the brim with human waste. Collection of “night soil” had long since stopped being a profitable endeavour as farms moved further away from the growing metropolis and cheaper guano fertilizer was discovered.

In 1849, John Snow, a London surgeon and early experimenter with anesthesia, published a tract On the Mode of Communication of Cholera putting forth evidence concerning the cholera outbreaks in recent years and pondering the idea that specific details did not support the miasma theory, but appeared to be related to water that had been contaminated by sewage, or by the “evacuations” of those already stricken by cholera. The publication failed to make any impact on what passed for public health authorities of the time.

John Snow

Five years later, on August 28, 1854, Frances Lewis, a five-month old baby girl, was afflicted with cholera. By the time she died on September 2, over three hundred people in the immediate Soho neighborhood had caught the disease and two hundred of them had died.   Snow lived only a few blocks away and went door to door in the neighborhood inquiring on the presence of cholera cases in each household. With this data, he did a very clever thing. On a map of the area, he made a tick mark at the location of each case of the disease. What jumped out immediately was the high number of cases adjacent to the public water pump at the corner of Broad and Cambridge Sts.

The data was not definitive. Still, Snow found answers to explain every anomaly. The Lion Brewery, located across the street from the pump, had no cases of cholera whatsoever. The brewery workers, it seems, had a daily beer allotment, and never drank from the pump. Similarly, the Poland Street Workhouse, with over 500 inmates, was located only a block north of the pump. Only five inmates came down with the disease, a much lower rate than in the rest of the neighborhood. The reason? The workhouse had its own well. Cholera cases from outlying areas were all found to have some connection to the Broad Street Pump, either from stopping by for a drink while out during the day, or in one case, a woman sending her servant down to the pump because she preferred the taste of the water from that well.

Snow’s map of the locations of cholera cases during the 1854 outbreak

To Snow’s mind, this data pointed towards some contamination of the water from the Broad Street Pump as being the source of the outbreak. But what sort of contamination? Snow’s theory, as outlined in his paper, was that cholera was spread through the “evacuations” of victims. It was later discovered that poor Frances Lewis’s mother had washed her soiled nappies and emptied the water in the cistern at the front of the house, a cistern that was found later to be less than three feet away from the Broad Street well.

Armed with this data, Snow asked to address the St. James Parish Board of Guardians and to speak of his findings. Although they remained skeptical of his ideas of disease contagion, they agreed, as an experiment, to his request–to remove the handle of the Broad Street Pump, rendering it inoperable.

A replica of the Broad Street Pump (Source: User JustinC, Wikimedia Commons)

The next day, September 8th, the handle was removed. And the number of cases of cholera dropped. It should be noted that the number of cases had peaked and was already dropping by the time the handle was removed. However, it should also be pointed out that Frances Lewis’s father was stricken with cholera on the very day that the pump handle was removed. If the pump had been still operating, it is likely that a fresh contamination of the water–and subsequent increase in new cholera cases–may have occurred.

John Snow is rightly regarded as the father of epidemiology, the study of the causes and transmission of diseases. However, in his lifetime, his work refuting the miasma theory was never fully accepted by either medical or political authorities. Not even after the Broad Street well and the adjacent cistern were inspected, and their design found faulty and their brickwork decayed. In the decade after the Broad Street cholera outbreak, Joseph Bazalgette would design and build the great London sewer system, whose sole purpose was to move the vast amounts of human waste generated by Londoners efficiently out of the city and far enough downstream that the incoming tide would not return it. Only then would London be rid of the dangerous miasma.

John Snow died of a stroke in 1858 at the age of 45. It is hypothesized that his early death was caused by kidney failure related to his self-experimentation with anesthesia. Indeed, had he not earned lasting fame from his work determining the means of transmission of cholera, he would have for his study and application of anesthesia. His renown was so great that Queen Victoria asked him to personally administer chloroform to her during the deliveries of her seventh and eighth children (Prince Leopold and Princess Beatrice, respectively). Acceptance of anesthesia by the Queen led to its acceptance by the medical community. And in 2013, the British medical journal The Lancet belatedly corrected its brief 1858 obituary of Dr. John Snow, finally praising him for “his achievements in the field of epidemiology and, in particular, his visionary work in deducing the mode of transmission of epidemic cholera.”