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In August 1854 London was in the grip of a cholera epidemic. Cholera gives rise to violent, profuse vomiting and diarrhoea which can lead to death within a few hours.


The above picture drawn at the time of John Snow shows the transformation in a woman within a few hours of contracting cholera

Medicine was more an art than a science in those days and most doctors thought that cholera was due to bad air –the miasma theory of illness. The germ theory of disease had yet to be elucidated [see my book P28- 34 Medical School Interviews The Knowledge]


Dr John Snow noted that a terrible outbreak of cholera took place in Broad Street, London. However the workers of brewery on the street were not affected. They apparently did not drink water, only beer. Dr Snow thought that the water might be contaminated and plotted cases of cholera on a map; he noted that even outlying cases mentioned that they obtained their water from the Broad Street pump. Snow ‘s  map was striking. The closer a residence was to the water pump in Broad Street, the greater the number of deaths – with a few telling exceptions coming from properties that had their own water sources. A nearby cesspit was leaking faeces into the pipes that supplied the Broad Street pump. Snow examined that pump water expecting to see contamination. The water looked pure and clear. The idea that tiny, invisible bacteria were the causes of diseases such as cholera had yet to be demonstrated by Pasteur and Koch [see my book p32]. However Snow remained sure of his case, largely because his collection of data had been so sound. He had the handle of the pump removed so people could not use it and cases of cholera fell. John Snow concluded that there was something in the water that caused cholera. This is thought to have been the first epidemiological study. Epidemiology is the branch of medical science dealing with the transmission and control of disease within a population.

John Snow was renowned for his honesty, hard work, thoroughness and humanity. He was also an early anaesthetist performing 11,000 chloroform anaesthetics without a single death. He administered chloroform to Queen Victoria during the birth of her son Leopold at a time when the Church, society and many doctors felt that pain, especially the pain of child birth had important lessons for the soul. The Queen however was beyond criticism and the fact that she had had an anaesthetic was important in the eventual acceptance of anaesthesia. He never sought fame and did not receive it in his life time but is now recognised as a true medical great. I’m more than happy to raise a glass [of clean water] to the father of the Science of Epidemiology – John Snow!