The 1854 Broad Street Cholera Outbreak
John Snow and his contribution to statistical studies and medical science
The year is 1854 — Soho, London, is a bustling place, much like the Soho today. Hawkers shouting their wares along the streets, and shops flaunting elaborate signs, waving their accolades and names in the English air. Workers can be seen walking (or riding) from home to work, and after their shift or day is done, from work to the pub for “a pint wit’ the lads”.
In the middle of the street, there stands a water pump at the corner of Broad Street and Cambridge Street, providing water to the households in the area — one of the heights of technology in those days. Today, a replica stands there in the original’s place, an ominous reminder of the outbreak that occurred over a century ago.
Image is in public domain.
In 1854, London was a well known city, and many of the buildings were of substantially good quality for their time, built to last except for the occasional fire or act of arson and vandalism. Soho was no slouch either, but in the 1800s, running water didn’t pipe straight into homes — families had to draw water from wells or pumps and bring them into their homes for various uses such as washing, cleaning, cooking and so on, hence the presence of water pumps in the street. This also meant that the modern toilets that are enjoyed today were not present in homes then, and families would remove their “waste” by throwing it into cesspits dug underneath their homes, or collected by “night soil collectors” to be dumped elsewhere (which unfortunately was often the River Thames, where other sewage lines led as well — this eventually led to a whole other problem on its ). One thing that was lacking in Soho, unlike many other areas in London and England, was the existence of a sewage system to remove septic waste.
In 1854, a terrible outbreak of cholera struck Soho, killing 616 people by the time it had run its course, and no one knew how it was being spread or how to control it.
Cholera and The Miasma Theory
Image Source: Wikipedia.org
Cholera was no stranger in those days — it was nicknamed “The Blue Death” as their victims would turn blue from their ruptured capillaries. Deaths from cholera were unfortunately quite common, and were quickly rising in tandem with public panic; so much that governments and institutions were offering hefty rewards for anyone who could come up with a way to prevent or cure cholera. But doctors were stumped, for no recognized theory of the day could explain the start and spread of the disease.
The miasma theory was then the prevailing medical theory of disease contraction and transmission — miasma, air containing particles called miasmata, was the reason for epidemics, and was known as a “noxious” or “poisonous” air, originating from rotting organic matter, and identifiable by a foul smell. Under this theory, individuals would fall ill as a result of being in the vicinity of miasma.
Picture of a hospital at Scutari, where Florence Nightingale worked to improve recuperating conditions for patients by improving air quality and ventilation — her justification for doing so was based on the miasma theory.
Image is in public domain.
Florence Nightingale, famous for her wartime nursing, was a strong proponent of the miasma theory, and improved the mortality rate of wounded soldiers by insisting that the recuperation areas to be kept well-ventilated and the air “as fresh as that of the outdoors”, in order to rid the hospitals of miasma. Under this theory, diseases were contracted from exposure to an environment containing miasma, and not through contact with other infected or diseased individuals — transmission from person to person was impossible.
It was for this reason that the Broad Street outbreak was so puzzling — infected people and households were nowhere near a graveyard or anywhere that would have been a source of miasma, nor were there any noxious fumes detected in the air. And yet, people were dying like flies — the death toll at the end of the outbreak has reached over 600, a large number for any town in those days, much less a built-up area.
John Snow, M.D.
John Snow (1813-1858), a y0ung but extremely accomplished doctor, was also living around the Broad Street area. As a young boy he had already proved himself highly intelligent, with a great talent in mathematics, and was already finishing his medical degree at the age of eighteen. Dr. Snow, known to be a vegetarian and one who religiously abstained from alcohol, was at this time highly devoted to his study in anesthesiology, which in those days was a new field, and finding more effective and less risky ways to dispense anesthetic (primarily chloroform) for use in childbirth or surgeries.
It was not the first time Snow had investigated cholera, nor the first time he doubted (indirectly expressed or otherwise) the validity of the miasma theory — he has shown an interest in the disease long before this outbreak, and had published a pamphlet with his speculations that, judging from the symptoms exhibited, cholera must be a digestive disease. This not only contradicted the miasma theory, but also the current idea that cholera was a disease of the blood. (It is also possible, although no documented evidence exists that this perspective had some roots in Galen’s theory of bodliy humors, which is in turn related to the practice of bloodletting.) This was in 1849 — 5 years before Broad Street would face their own concerns with cholera.
Cholera Case-Counting
As puzzling as the outbreak was, one might suspect that the difficulty of the problem coupled with the severity, only spurred Snow to study the transmission and the source of the disease even more passionately — the fact that he, too, lived on Broad Street would lend a personal interest to solving this mystery. Snow started knocking on doors, one by one, and interviewing the occupants of the house — finding out whether they had any members of the household who were ridden with cholera, and other details that he might have deemed essential to his investigation. Without knowing it, Dr. Snow was the first one to start the practice of medical cartography, by drawing his own map of Broad Street.
Image Source: Wikimedia Commons
The distribution of the cholera cases seemed to concentrate in the Broad Street area, strengthening Snow’s view that cholera was transmitted via the oral-fecal route. The common focus in most of these cases seemed to indicate that the pump on Broad Street was the center of the spread. There were, however, exceptions to this rule, which at first seemed to point out a flaw in the theory — the workers at a nearby pub were almost completely clear of cholera cases, while some other cases occurred in the adjacent neighbourhoods with their own water pumps, far away from Broad Street (see map above). This seemed to imply that there was no correlation between location and incidents.
That is, until John Snow examined more evidence.
Whether this was part of a follow-up investigation in response to the seemingly random distribution of cases, or that John Snow had asked for the exact source of water on his initial round of interviews and door-knocking is not known. However it was, Snow managed to gather that one thing that just about all cases had in common was indeed…
The Pump On Broad Street
Image source: Wikimedia Commons
This water pump, which was said to have cooler water than the other nearby pumps was so popular that workers and schoolchildren from surrounding neighbourhoods would stop by the pump to have a drink of the water along their journey, and some families who moved from Broad Street to other nearby communities would make the additional walk to their preferred source of water. This explained how the people from the adjacent neighbourhoods contracted cholera (and then possibly spread it in their own neighbourhoods, although this is not documented explicitly). The clincher to this was the case of Susannah Eley, who was reported to have “retained a fondness for Broad Street water and regularly had it delivered to her home”, easily explaining her death and the unfortunate demise of her visiting niece.
What of the workers in the Lion Brewery, situated merely across the street from the pump? Water, although relatively safe to drink compared to earlier days, was perhaps not the preferred choice of beverage for adult men — it was certainly the case for these workers, who much preferred the alcohol and liquor offered them as part of their fair wages. Still other building occupants or households avoided contracting cholera by drinking from a private well.
Statistically speaking, there was no other discernible increase in the number of cases of cholera in that part of London (cholera was common but not common enough to result in the epidemic in Broad Street), aside from those related to drinking from the Broad Street pump — Snow managed to convince the authorities to remove the handle from the pump, thus enforcing its disuse, and the number of cases dwindled to a much lower level. Further investigation of the well indicated that it was dug very close to cesspools, which might have leaked into the well and therefore caused the outbreak.
“They can’t handle the truth”
Despite all evidence against the miasma theory and the proof that cholera was transmitted via the oral-fecal method, the medical community was not as enthused as Snow was to renounce it, saying they saw no reason to adopt this belief, and that there was insufficient evidence to show that the water in the Broad Street well was contaminated by the cesspools and sewage. The local authorities themselves declined to release Snow’s conclusion to the public, under the pretext that it would be too much for the general populace to stomach (pun intended). Some societies, however, recognized that there were no other explanations aside from Snow’s that could explain the spread and cause of cholera in some cases, and acknowledged such without affirming Snow’s theories.
Image source: Wikimedia Commons
A pub named after the doctor himself, at the original site of the Broad Street Pump. Also pictured is a Blue Plaque, placed by the Royal Society of Chemistry in 2008 as a ‘National Chemical Landamark’ states: “Dr John Snow / (1813-1858) / Founding father of Epidemiology. / In 1854 his research linked / deaths to the water pump / near this site and thus / determined that cholera is / a water borne disease. / 16 June 2008".
Image source: http://himetop.wikidot.com/the-broad-street-pump-original-site
John Snow’s Legacy to Medicine and Mankind
In the conducting of his experiments, John Snow started the beginnings of what would later be germ theory, but also pioneered various methods of observation — one will note that his study of the source of cholera required no direct medical background aside from knowledge of the symptoms of the disease (microbiology and virology had not yet been established), Snow utilized no advanced form of observation apparatus such as microscopes, and relied simply on mathematical statistics and reasoning. Today, the method is known as medical cartography. This changed and improved the approach to investigative study
Snow’s protests to the “proven” and “accepted” medical theories of that time ring familiar even to scientists today — having had a good age of technological and scientific advancement, it may come as no surprise that most “learned” men rested on what they thought were proven theories, without ever testing them. Cases such as the miasma theory had partial basis and validity to them, but, as can be seen, were an incomplete description. Snow’s action then also serves as a reminder that even the most sturdy sciences are subject to scrutiny from time to time, and may be built upon, dissected, or even disproved with new knowledge.
Unfortunately, Snow did not live to see his successes — he passed away on 16 June 1858 at age 45, only a few years after the Broad Street Outbreak. Even then, his claims were still not accepted and it was only later that various societies and scientists confirmed his work and awarded him recognition posthumously.
