Advances in medical science are often made by the most unlikely people. Sometimes they are outsiders or more likely they are involved or trained in another discipline. The person making the breakthrough is usually mercilessly vilified by the gatekeepers of the status quo. Ultimately the discovery is adopted without so much as a muted apology from the previously virulent detractors. So it was with cholera.

Main picture: John Snow

During the nineteenth century, recurrent outbreaks of cholera would claim the lives of a huge number of people; not only the young, the elderly and sickly but even those in rude health. The accepted wisdom was that the cause of this deadly disease was the quality of the air. Blame was apportioned to miasma or bad air. With the advent of the Industrial Revolution, the quality of the air in Great Britain had declined precipitously. Blaming the contagion as being air borne was not fanciful but neither was it based on any facts. The recommended treatment only exacerbated the patient’s decline. By drawing blood, the rapid loss of body fluid caused by the cholera bacteria swiftly resulted in the collapse of the victim’s internal organs.

Like most doctors of the day, John Snow left school before completing his schooling. At 14 John Snow was apprenticed to a surgeon, William Hardcastle in Newcastle upon Tyne. It was here that he first encountered cholera which devastated the town. His curiosity had been piqued but it was whilst working as an assistant to a colliery surgeon at two separate collieries that John came to believe that it was the water that was the carrier of the disease and not the air.

With this lamentable state of affairs of recurring pandemics scything through the population, John Snow, a recently qualified doctor, held a contrarian view on cholera’s cause. He speculated that the source of the infection was not miasma, but the quality of the water. As the germ theory of disease had not yet been developed, the exact mechanism by which water spawned cholera was unknown to him.

I am unable to trace the factor that was decisive in Snow attributing the water and not the air to the spread of cholera yet I am of the belief that by working at different collieries and by deliberately going underground into the fetid stale air, his lively mind noted some differences in the rate of infections or even those affected which his theory.

Snow tests his hypothesis

In 1837 Snow moved to London and commenced working at the Westminster Hospital. With his interest in cholera, Snow became one of the founding members of the Epidemiological Society of London which was formed on the outbreak of cholera in 1849. During this year, Snow first publicised his theory but it was not until a cholera outbreak in Soho in London during 1854 that a real-life example was incorporated.

In the sphere of public health, this pivotal research became known in Britain as the Hand Pump in Broad Street.

Suspecting that a hand water pump located in the vicinity was the cause of the cholera epidemic, Snow traipsed from door to door to record the pattern of the cholera deaths. On a map of the area, he marked a rectangle against every house to signify a death from cholera. The epicentre of the deaths was a hand pump in Broad Street, now called Broadwick Street.

Even though a microscope, examination of a water sample did not conclusively prove its danger, the pattern of the disease was convincing. However some perplexing anomalies were noted:

• None of the workers at a local brewery had contracted cholera
• A family outside the Broad Street area had died from cholera

• Finally there was another significant anomaly. None of the monks in the adjacent monastery contracted cholera.

John Snow memorial and public house on Broadwick Street, Soho

On enquiry all the exceptions had logical explanations:

• The brewery workers only drank beer during their 12 hour shift. In spite of utilising water drawn from the same polluted water source, the fermentation process must have resulted in “purifying” the water.
• The family outside the Broad Street area had used that water as they considered it sweeter than their local water.
• Investigation revealed that the monks were also not an anomaly but rather as further evidence for they drank only beer, which they brewed themselves.
  

Based upon the generally accepted miasma theory, the Local Council was not convinced that water was the carrier of cholera. Notwithstanding that, the pattern of the disease as determined by Snow was convincing enough to persuade the local council to disable the pump by removing its handle.

Post script

Like all Pioneers in whatever discipline, Snow’s proposal had only been accepted as a matter of expedience. When the epidemic abated, they replaced the Broad Street pump handle as they rejected Snow’s theory. To accept his proposal would have meant indirectly accepting the oral-faecal method of the transmission of disease, which was too unpleasant for most of the public to contemplate

Conventional wisdom has triumphed again.

This episode culminated in the construction of London’s underground sewerage reticulation system

His most vocal antagonist was William Farr. It was to take Farr another 12 years before he admitted the veracity of Snow’s ideas. This arose when he investigated another outbreak of cholera, this time at Bromley by Bow. He was forced to issue an immediate instruction that no unboiled water was to be drunk.

To further vindicate Snow, researchers much later discovered that this public well had been dug only 0.9 m from an old cesspit, which had begun to leak faecal bacteria. The nappies of a baby, who had contracted cholera from another source, had been washed into this cesspit. Its opening was originally under a nearby house, which had been rebuilt farther away after a fire. The city had widened the street and the cesspit was lost. It was common at the time to have a cesspit under most homes. Most families tried to have their raw sewage collected and dumped in the Thames to prevent their cesspit from filling faster than the sewage could decompose into the soil.

William Farr – almost John Snow’s nemesis

The transformative consequences of Snow’s discovery were huge. Shortly thereafter London embarked on a massive building project to create the first city-wide sewerage system.

The construction of sewers combined with the chlorination of the water supply ultimately eradicated the scourge of cholera.

I will drink to that.

Bring me a beer.

Cheers.

Better safe than sorry.

Source

Steven Johnson’s 2006 book The Ghost Map: the Story of London’s Most Terrifying Epidemic, and How it Changed Science, Cities and the Modern World is a highly entertaining account of the epidemic and Snow’s analysis of it.