Dr. John Snow and the Broad Street Pump – Chhada Nathan Kabariti

The prevailing theory during the cholera outbreak of 1854 was that infectious and contagious diseases were spread by a general miasma: a pollution of the atmosphere that became malignant when combined with the emissions of organic decomposition from the earth. The miasma theory was very appealing to English sanitary reformers. It explained why these fatal diseases were epidemic in the filthy and stinking areas inhabited by the poor. At the time, people believed in the miasma theory and protected themselves by inhaling sweet scented things. It was within this framework that Dr. John Snow was working and it would be another generation before Louis Pasteur and Robert Koch discovered that diseases were actually spread by germs.

One of the most famous landmarks in London’s medical history located on Broadwick Street is the Broad Street Pump, which was a pump in the center of the slums and rookeries in Soho in 1854. On September 8, 1854, the handle to this pump was removed on the instructions of Dr. John Snow so that water could no longer be drawn from it because Snow recognized the water from this pump was the source of the cholera epidemic in Soho.

As is often the case in medical and scientific breakthroughs, the stories created around them are not the way it was. The version of the John Snow story that we hear these days is that by removing the handle from the Broad Street pump, Snow saved countless lives in the middle of a cholera epidemic. By identifying the water in the pump as the contagion, he moved away from the original theories of miasma and air pollution to the more modern theory of germs, bacteria, and infection. Finally, that it was John Snow’s work became the main impetus for the extraordinary revolution in London’s sanitation that happened over the next decade.

What was groundbreaking about John Snow’s work was the statistical method behind it. He started plotting the locations of all the deaths in the cholera epidemic, and he discovered that nearly all clustered around water pumps, particularly around the pump on Broad Street. He then investigated the people who were living in the slums around Broad Street and found that the people least affected were the brewery workers because they were drinking beer, rather than water.

Although John’s statistical work was groundbreaking, the great moment of the pump handle removal had very little effect and it was rather largely symbolic. By the time he managed to persuade the officials to remove the pump handle, the cholera epidemic had nearly burned itself out anyway, so it is unlikely he saved any lives. In addition, the idea that his work was pivotal in the campaign to revolutionize London sanitation is unfortunately not true. Snow’s work, when he finally produced it, managed to garner little attention at the time. The supporters of the miasma theory were unconvinced by Snow’s findings due to the absence of an organism and the lack of conclusive experimental proof. While the organism (Vibrio cholerae) had been discovered in 1854 by Italian anatomist Fillipo Pacini, nearly all English scientists and physicians were unaware of his work.

In hindsight, John Snow’s work has been recognized as a very important contribution to a public health movement that had been growing in London since cholera had arrived in the early 30’s. The real significance of John Snow story is that it is the birth of epidemiology and statistical analysis, and it shows how many lives you could potentially save and how you can improve conditions with proper statistical surveys. Of course this is something we recognized clearly now but was not recognized at the time. Therefore, although John Snow went on to make other medical discoveries, he never really lived to see his work on the Broad Street pump come to any practical fruition.

London provides an example of how useful a wrong theory (miasma) can be for addressing an epidemic (improvement of air, solid waste and water supplies). While the sanitary reforms following the miasma theory were effective at containing cholera, full acceptance of the scientifically valid germ theory would have saved even more lives.

Chhada Nathan Kabariti