The Broad Street cholera outbreak: how bad was it and how was it contained?

In 1854, amidst a major cholera pandemic, London physician John Snow made a deduction that would save countless lives – that the disease was not spread by 'bad air', but by germ-ridden water. This is how he brought the Broad Street cholera outbreak under control...

Photograph of John Snow in 1856

On the evening of 7 September 1854, the eminent doctor John Snow spoke to a council of powerful men. Cholera outbreaks had been ravaging London for the past few years, claiming the lives of almost 15,000 people, but nobody had figured out how to stop it. Snow, a physician from Yorkshire, saw what none other could see – that the disease was transmitted in water.


Presenting his compelling evidence to the local authorities, he convinced them to take action, and they responded by removing the handle of an infected water source. Snow saved many lives that day, but his quest was a long one, and it was far from over.

Who was John Snow?

Born to working-class parents in a poor neighbourhood of York, Snow was one of nine children. His intelligence was spotted early on, and at age 14, he began to work as a medical apprentice. He earned a pittance, but the experience he gained there would be invaluable, as he gained a detailed insight into the pathology of cholera.

Sbnow graduated from the prestigious University of London in 1844, and in 1849 wrote a controversial pamphlet titled On the Mode of Communication of Cholera. It defied the conventional belief that cholera (a disease that had arrived in Europe from Asia) was an airborne disease, spread by mysterious ‘miasmas’ that polluted the air with a strange killer disease. He hypothesised that the disease was carried in water sources, which had come into contact with cholera via the excrement of infected persons.

This theory was difficult to swallow, and many of his peers dismissed his ideas as “peculiar”. But Snow’s theories were not so far-fetched. Victorian London was an incredibly unsanitary place, and the Thames was the stinky centre of it all.

At this time, London’s famous sewer systems were incomplete, and much of the populace dumped their sewage into the river directly or in poorly maintained cesspools. Indeed, almost every house in London had one of these noxious holes directly beneath it.

When was the Broad Street cholera outbreak?

Now living in the grubby capital himself, Snow witnessed firsthand the impact of cholera on the city. To prove his theory, he began work on a “grand experiment” in 1853. This would measure the death rates of those living in places with contaminated Thames water, compared to those living with uncontaminated water. When cholera struck close to his Soho home the next year, Snow saw the opportunity to turn his neighbourhood into a case study.

Snow found opponents in every corner. The idea that cholera came from faecal bacteria, ingested by its victims, was too disgusting for the public to stomach

After convincing a sceptical local priest about his theory, Snow interviewed households who had been impacted by cholera to garner information about where they got their water.

He placed dots on a map of the area to show where cholera cases had occurred, and noticed that they had one thing in common – they were situated close to a pump on Broad (now Broadwick) Street, supplied by the Southwark and Vauxhall Waterworks Company, who were known to have taken water from polluted sections of the Thames. There were a few anomalies – such as the local brewery workers who mostly drank beer and their own water supply – but the evidence painted a clear picture.

Snow rushed his evidence to the parish board, begging them to hear him. The council was soon persuaded to remove the handle of the problematic water pump. Within days, the number of cholera cases began to decrease.

In 1855, Snow published a lengthy pamphlet on his findings during the outbreak. He found that the pump’s well had been dug just a few feet away from a putrid cesspit, into which the nappy of a baby (who had contracted cholera from elsewhere) had washed. The waste water had leaked into the well, causing the disease to spread exponentially.

Unrecognised genius

Still, Snow found opponents to his theory in every corner. The idea that cholera came from faecal bacteria, accidentally ingested by its victims, was too disgusting for much of the public to stomach. Additionally, his work presented a challenge to the capital’s powerful water companies, and the government swiftly dismissed his theories.

Tragically, Snow died just four years after his 1854 breakthrough. While at his desk one day he had a stroke, and died aged 45. It was not until 1866 that Snow got the validation he deserved, when one of his old adversaries, Dr William Farr, proved that cholera was a waterborne disease.

Nowadays, Dr John Snow is regarded as the founding father of epidemiology [the study of how disease acts within a community], and as a man whose ingenuity placed him far ahead of his time.


This content first appeared in the September 2017 issue of BBC History Revealed