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John Snow: medical detective

15 Mar, 2013
John Snow, 1856.

John Snow, 1856.

As the world celebrates the bicentenary of John Snow’s birth, Jimmy Whitworth reminds us how an inquisitive Victorian came to profoundly change public health.

During March and April of this year, the Wellcome Trust will be participating in a number of events organised by the John Snow Society to celebrate the 200th anniversary of the birth of John Snow. But who is John Snow? No, not the newsreader, nor the Sussex fast-bowling cricketer, but a life-long bachelor, a teetotalling doctor from Yorkshire. I expect that if he were born today he would be a non-smoking vegetarian too.

Dr John Snow was a polymath, with interests in a wide-variety of topics. He was fascinated by anaesthesia, a newly discovered technique that promised to transform the horrors of surgery of the day. He was particularly interested in chloroform and conducted a number of experiments culminating in administering chloroform to Queen Victoria while she was in childbirth. Victoria, an obstetric veteran, was recorded as commenting on ‘the blessed chloroform’, a remark that has been commemorated in the annual Blessed Chloroform Lecture organised and held on occasion by anaesthetic members of the John Snow Society.

But John Snow is most remembered today for his pioneering work in epidemiology, a discipline that he more or less invented. He was thrown into the midst of a cholera epidemic in Soho, London, near his place of work, and he was determined to find the source of the outbreak. Remember that this was at a time before acceptance of Germ Theory, and it was generally held that most diseases were caused by a ‘miasma’ in the air. Snow noted that there was a clustering of cases around Broad Street (now Broadwick Street) but that not everyone in the neighbourhood was affected. In fact it was the outliers and anomalies that nailed his hunch that drinking water from a public water pump was the source of the epidemic. 

L0003055 Map of Soho showing deaths from Cholera, 1854.

John Snow’s map showing deaths from Cholera in Broad Street, Golden Square, and the neighbourhood, from 19th August to 30th September 1854.

The story reads like a modern-day detective drama, and indeed it is the sleuthing element of epidemiology that draws many of us to the discipline. He noted that none of the employees of the nearby brewery were affected, but he discovered that they had their own deep well on the premises from which they took their water. There was also a case in West Hampstead many miles from Soho. Could this case be linked to the epidemic or was it from a different source? John Snow found out that the woman in question, the ‘Widow of Hampstead’ was particularly fond of the taste of the water from this particular pump in Broad Street and so her son’s used to send her a flask of the particular water by horse and cart on most days (talk about fatal filial devotion!). John Snow was therefore able to link this case to the pump as well, and convinced of the source of the epidemic he went straight to the local authorities, provided his evidence and persuaded them to remove the handle of the pump so that nobody could use it any more. The epidemic quickly died away until it reappeared in another part of London the following summer. In fact, the epidemic was probably dying out by the time the pump handle was removed, but why spoil a good story. Epidemiology members of the John Snow Society commemorate this event through the Pump Handle Lecture held in early September each year.

John Snow’s name is famous throughout the world. The main lecture theatre at the London School of Hygiene and Tropical Medicine is named the John Snow Lecture Theatre, a well-known public health consulting agency is named John Snow Inc., and his name is commemorated in various ways at the Centers for Disease Control and Prevention in Atlanta, Georgia. Snow was one of those wonderful go-getting Victorians with an enquiring mind, and in his case his pioneering work has contributed to public health, sanitation, safe anaesthesia and made very many people’s lives safer and more comfortable.

Come along and join us at one of the events in the coming weeks.

Jimmy Whitworth

Dr Jimmy Whitworth is Head of International Activities at the Wellcome Trust.

Find out more about the John Snow Society and their bicentenary celebrations.

Image credits: Wellcome Library, London

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