John Snow and cholera: how myth helped secure his place in history
By Sandra Hempel
The high-profile marking of John Snow’s bicentenary on the fifteenth of March would have surprised the great man. The London School of Hygiene and Tropical Medicine, the WellcomeTrust, and The Lancet were among the august UK organisations to honour him with events including an exhibition, three days of seminars, and a gala dinner. The physician was also celebrated in the United States where he has a large fan base.
By the time of his death, on 16 June 1858 at the age of 45, Snow was convinced beyond doubt that his theory on the mode of transmission of epidemic cholera was correct but had little expectation that any credit would accrue to him. His friend, the Soho curate Henry Whitehead, said Snow predicted that he might not live to see the day when great cholera outbreaks were in the past — which was true — and also that his name would be forgotten when that day came, which was not. On the contrary, he is now widely regarded as the father of the science of epidemiology, with his life and work the subject of countless books, articles and web pages, while 200 years after his birth his legacy remains the focus of lively academic debate.
But it’s an unfair world. Achievement alone isn’t always enough to ensure that an individual, however deserving, secures a place in history and in Snow’s case, myth had a role to play. Not that Snow appeared at all interested in fame, posthumous or contemporary. Another friend, Josuah Parsons from his student days, remarked: “The naked truth for its own sake was what he sought and loved. No consideration of honour or profit seemed to have the power to buy his opinions on any subject.” That was just as well, for both honour and profit were in short supply, at least where his groundbreaking work on epidemic disease was concerned.
By the mid-1850s when Snow published his seminal work on cholera he was enjoying some success in the fast-developing specialism of anaesthesia, even attending Queen Victoria at the birth of two of her children. His thinking on disease was largely ignored, however, mainly because he rejected the then widely accepted belief that foul air, or miasma, was to blame. He reasoned, correctly, that cholera was spread when some of the matter thrown off by a victim — the vomit or the massive cloudy discharges from the bowels — found its way into a healthy person’s mouth. He also explained the disease’s frightening habit of striking hundreds of people simultaneously without warning: the cause was infected sewage leaking into the water supply, a common occurrence in the first half of the 19th century. He was not believed.
In the summer of 1854 in order to test his theory Snow carried out what become known as the Grand Experiment, tramping the streets of South London while the country was in the grip of its third cholera epidemic, knocking on doors and asking which of two water companies the householder used. He discovered that customers of the company that took its supplies untreated from the Thames, right next to where the sewers of London were discharged, were between eight and nine times more likely to die of cholera than those whose supplier had recently moved its source upriver, out of reach of the filth.
It was as Snow was putting the finishing touches to this work that he became involved in the Broad Street episode. His serious academic reputation is largely based on the South London research, but it is Broad Street that has contributed most to his enduring reputation, linking as it does a compelling story with two icons — a “death map” and the image of a street pump — with the addition of a little fiction along the way.
Overnight on Thursday, 31 August 1854, 200 people in a tiny part of Soho around Broad Street and Golden Square were struck down by a massive explosion of cholera, the fastest and most deadly ever seen in Britain. Whole families were carried off together. The epidemic continued for 10 days, still confined to a few streets, before petering out. The eventual death toll was over 600.
When Snow heard what was happening, he first looked at the addresses where the fatal cases had occurred and then went on to pioneer what is now a vital tool in epidemiology, disease-mapping, marking the deaths, house by house, on a street plan. The map showed just how local the outbreak was; all the deaths clustered in and around Broad Street. What interested Snow, however, was that those deaths either plummeted or stopped altogether at every point where it was easier to go to another pump than the one in Broad Street.
On the night of 7 September then, a week into the epidemic, Snow gate-crashed a parish meeting at St. James’s church, Piccadilly, where the Board of Guardians responsibly locally for public health were discussing the outbreak. Polluted water from the Broad Street well was to blame, he told the Guardians. They must put the pump out of action.
So far, all true. At this point in some accounts though a little creative licence creeps in. After a bitter row with the recalcitrant authorities, we are told, Dr Snow then storms off, either to chain up the pump handle himself or wrench it off with his own hands. In fact while the authorities were far from convinced, they did take Snow’s advice and the pump was disabled.
The next piece of fiction is that the deaths then stopped in their tracks and, hey presto, overnight John Snow was vindicated. Truth was, the epidemic had already peaked of its own accord; putting the pump out of action proved nothing. The longer, more complex story of how John Snow was proved right is actually more interesting but it’s easy to see why such a satisfying ending to the tale has evolved. And if myth has proved helpful in ensuring that a brilliant man who was dismissed and reviled during his lifetime is now so rightly celebrated, it’s no bad thing.
Sandra Hempel is a writer and editor who specialises in health and social issues. Her book The Medical Detective – John Snow, Cholera and the Mystery of the Broad Street Pump won the British Medical Association book award for the public understanding of science and the Medical Journalists’ Association book award. Her next book The Inheritor’s Powder, which looks at arsenic poisoning and forensic toxicology, is published by Weidenfeld and Nicolson on 13 June 2013. She recently gave a talk at the London School of Hygiene and Tropical Medicine about John Snow.
Throughout the year, the International Journal of Epidemiology will be publishing special reprints marking John Snow’s bicentenary, including The Siege of Krishnapur by J. G. Farrell and Cholera, with reference to the geological theory: A proximate cause – a law by which it is governed – a prophylactic by John Lea. The IJE is an essential requirement for anyone who needs to keep up to date with epidemiological advances and new developments throughout the world. It encourages communication among those engaged in the research, teaching, and application of epidemiology of both communicable and non-communicable disease, including research into health services and medical care. OUP publishes the journal on behalf of the International Epidemiological Association.
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Image credits: (i) John Snow, seated, resting right arm on table, anon. (ii) ‘A cholera patient’, caricature of a cholera patient experimenting with remedies (Robert Cruikshank’s random shots No. 2) (iii) Street Map of Soho, around Golden Square, illustrating incidences of cholera deaths during the period of the Cholera Epidemic, 1853. All three images are used with permission from the Wellcome Trust. Do not reproduce without express permission.