John Snow: The sleuth of cholera
The industrial age made England not only a filthy rich kingdom but also plain filthy. A gut-wrenching disease then snuck in, and only a teetotaler physician can see its nature past the mist.
I suspect almost all of us already know who Jon Snow is. Perhaps some of us know him from devotedly watching the Game of Thrones series, which is now somewhat taboo to mention after the disastrous last season. Others may know him not from watching the series — and blissfully spared from the fate that befell the series’ devotees — but from a popular meme of him, saying: “You know nothing, Jon Snow!” Perhaps you, as I was, also knew nothing about an entirely different person whose name is homophonous with the GOT character: John Snow.
The physician and the overseas disease
So, who is he? While Jon is a badass royal who faced off the undead army White Walkers, John was a brilliant English physician who spent half of his life fighting against an arguably more lethal enemy: cholera. Born into a coal labourer’s family today in 1813, his parents saw that their first son’s mind transcends their setting. They then took a decision to send little John to school with what little money they had. At age 14, he became a doctor’s apprentice stationed in Newcastle. Studying diligently under the tutelage, Snow encountered his mortal foe four years later when the first cholera outbreak hit England in 1831.
Cholera was a terrifying illness, especially when people did not yet grasp what it really is. The affected people will grab their stomach and start spewing vomit and watery diarrhoea profusely. The expelled amount is so intense that it will dry them out in a matter of hours — marked by wrinkled skin and sunken eyes. They lose so much bodily liquid — also known as the hypovolemic shock — that their blood thickens and ceases to flow throughout the body. The death then ensues.
Nowadays, we know cholera is a bacterial disease of Vibrio cholerae, transmitted through faecally contaminated water. This bacteria enters the body through ingestion and infects the small intestine. However, back then, the most learned minds clung to the obsolete miasma theory in order to explain cholera transmission. The theory states that the disease is caused by “bad air” — miasma itself means pollution in Greek — emanating from rotting sources like graveyards.
Snow thoroughly analysed every observation of lives that he couldn’t save or treat properly in the first outbreak. He was one of the first to realise that the disease finds its way to the body by ingestion rather than inhalation. Suspected water sources, he did a comparative case study where he analysed two resident groups who each obtain their water from two wells; one mixed with waste and the other is not. True to his hypotheses, almost all inhabitants with the filthy water source contracted the disease. He painstakingly gave a full description of it in his paper “On the mode of communication of cholera”, published in 1849.
The once stink and filthy London
It is so obvious for us today that we can easily get ill from drinking filthy, contaminated water, but this was not always clear for the London populace in the mid-19th century. Kickstarted by the Industrial Revolution, working on fields needed fewer people as new farming technologies were gradually used. People increasingly migrated to urban areas — one of them is London — where jobs are abundant.
The problem is, London was not ready to facilitate a clean environment for the large influx of people. It only had cesspools for waste disposal; sewer systems had not been well-spread and structured. So if their cesspools were overflowed, people shoved their waste — including poops — into their streets or dumped them into River Thames. All streets were littered with bodily waste, and the now pristine river was unceremoniously dubbed as ‘The Great Stink’ due to its worsening smell.
In summary, people acclimatised themselves to this rather unsanitary way of life. Therefore, the majority of people found it hard to accept that their habit and environment highly contribute to the spreading of cholera instead of invisible particles in the air. That is why the health boards dismissed Snow’s findings, possibly said to the well-intentioned man: “You know nothing, John Snow!” But Snow had not thrown the towel yet, and he was determined to garner more concrete evidence.
Sherlock Holmes of Broad Street
He got his chance when a cholera outbreak stroke Soho district in 1854. Having suspicion on wells, he mapped every water source in the area and made sections according to each residence’s proximity to their nearest well. This mapping technique is what we called today the Voronoi diagram. Peered at his map, Snow then noticed that the Broad Street water pump has the most victims with some false-positive and false-negative cases.
He then garnered data and evidence from the locals with the aid of Henry Whitehead — the community’s curate — to clear up the incorrect indications. For the false-positive cases — locals who lived at a close distance from the Broad Street pump but did not contract cholera — one is a workhouse with its own water source, and the other is a local brewery where the men drank beers only. For the false-negative cases — locals who lived far from the pump and contracted cholera anyway — they were children and workers who went to their respective school and work by passing Broad Street and often took a gulp from the pump. All cases were valid!
Armed with mounting corroboration, Snow wrote an exhaustive report about the danger of the Broad Street pump. His effort finally convinced the local health commission to remove the pump handle, and the outbreak burnt out. It was later found out that there is a leak to its water source from a poorly-built cesspool. This cesspool was filled with diapers from a baby who recently died from cholera, and most possibly, he was the index case in that neighbourhood.
Never was a quickly content person, he conducted another investigation to two water companies in other parts of London. One company pumped its water nearby where the sewage was spilt; the other had its water from a cleaner location upstream. As expected, cholera infected far more people who consumed the water pumped close to the sewage dump, where the bacterias reside. Cholera did transmit through the water all along!
Overarching legacy
The way Snow conducted his research — investigating and accumulating the sources, finding out the transmission, mapping the affected demography — was a new look to study diseases. Therefore, the doctors can now take preventive action such as fending off or containing the infection, not merely examining the patients after they get sick. These methods are the bedrock of what we know today as epidemiology.
However, even with his proof-laden reports, his cholera transmission theory still was not warmly received. The miasmists were still lingering to their obsolete theory, and it took years later for people to finally accept the germ theory infection — via Robert Koch and Louis Pasteur. Snow continued to work on his investigation after the 1854 outbreak, but four years later, he died at a relatively young age, 45 years old, from a stroke.
Now, Snow was an accomplished and respectable physician. He was admired by many of his peers, and he refined a safe use of anaesthetics. In fact, he was the entrusted doctor to administer Queen Victoria with anaesthesia when she gave birth. Twice. It was just that his work over cholera uprooted the lousy habit and old thinking of England society at that time, and therefore it was a pill too bitter to swallow for many.
But he was a giant, lending his shoulder to the future reformers who bent on making the world a better place. Apart from inspiring Koch and Pasteur, Snow’s work accelerated the sanitary movement in England. The core of this movement is the sewer network system, headed by civil engineer Joseph Bazalgette. While he did not see this when he was alive, Snow’s legacy leaps far — until today, even.
And today, we commemorate him on his birthday. For everyone who struggles to ameliorate the world and fears that they will not see the end of their quest, know that the future will always value your legacy highly.
