EHJ October 2004, pages 305-307
Wednesday, 8 September 2004, marked the 150th anniversary of Dr John Snow removing the handle from the Broad Street water pump in Soho, London. Rob Couch sketches a portrait of the father of epidemiology and the pioneer of anaesthesia

On 7 September 1854, one of the most important meetings in the history of public health took place. The board of guardians for the parish of St James in London's Soho had gathered to discuss how to handle one of the worst cholera outbreaks the parish had ever seen. That year, cholera had hit Lambeth and Southwark in the capital. Despite Soho being so unsanitary, with waste from cowsheds, slaughterhouses, grease boiling dens and cesspits creating a festering public health timebomb, the area had initially remained relatively untouched by cholera. Then five days before the meeting, 127 people living in or around Broad Street died, causing three-quarters of residents to flee their homes. Within days, 600 were dead with over 12 per cent of residents in some parishes claimed by the disease.

One can only imagine the fevered conversation among the elected board of governors responsible for public health on that fateful day when a stranger asked to be allowed to address them. A local doctor, Dr John Snow, entered the room. His friend Dr Edwin Lankester, described what happened next: "In a few words, [Dr Snow] explained his view of the head and front of the offending. He had fixed his attention on the Broad Street pump as the source and centre of the calamity. He advised the removal of the pump handle as the grand prescription. The vestry was incredulous but had the good sense to carry out the advice. The pump handle was removed and the plague was stayed."

This event marked the birth of modern epidemiology. And to celebrate the 150th anniversary of the removal of the pump handle on 8 September 1854, the John Snow Society this year organised a guided walk and the twelfth pump handle lecture at the London School of Hygiene and Tropical Medicine.

John Snow was born on 15 March 1813 in York, his birth just preceding modern germ theory in which miasma - the theory of bad or malodorous air as a cause of disease - dominated. Aged 14, Dr Snow began a medical apprenticeship, under the Newcastle surgeon William Hardcastle.

At 17, he became a vegetarian and a supporter of the temperance movement. Alcohol consumption in 1820s England was widespread, especially among the poor, because for most people, alcoholic drinks were the only safe and readily obtainable thirst quencher. Drinking water was usually contaminated and scarce and tea was too expensive. It is likely that, because of his eccentric lifestyle, Dr Snow's colleagues may have regarded him as something of a crank. It is also ironic that the most visual reminder in 2004 of Dr Snow's work in Broad (now Broadwick) Street is the John Snow public house. Dr Snow may, however, have approved of his pub namesake since the low number of cases at the local brewery, which had a private well, was one factor that helped prove his theory that cholera was being spread by the water at the Broad Street pump.

Dr Snow's first experience of cholera was the arrival of the disease in Newcastle in December 1831, after hitting Sunderland's port some two months earlier. Some 1,330 cases and 801 deaths occurred in Newcastle and Dr Snow was dispatched to Killingworth Colliery, site of a significant outbreak. He later described the mine as "one huge privy where the men ate without washing their hands". He also recalled men being attacked by cholera while at work - early observations that may have led him to suspect a faecal-oral transmission route.

In 1836, Dr Snow enrolled at the Great Windmill Street School of Medicine in Soho. Founded by the anatomist Dr William Hunter, the school - on the site of the present Lyric Theatre - became one of the most prestigious private medical schools in London. Dr Snow qualified as a member of the Royal Medical Chirurgical Society in 1838 and soon moved from his lodgings at 11 Bateman Buildings, Soho, to nearby 54 Frith Street. This house is now known as 61 Frith Street following past street renumbering. It also suggests Dr Snow's commemorative plaque may presently be on the wrong house - a possible error the John Snow Society is investigating.

A life-long learner, Dr Snow graduated as bachelor and later doctor of medicine of the University of London and became an active member of many London medical societies, giving him ample opportunity to communicate his research. But his friend Richardson, cited in Snow Society in 2004, described Dr Snow as a poor speaker with a husky voice. "He always spoke to the point but found it difficult to obtain a favourable notice."

The year 1848 witnessed many public health milestones, including the first Public Health Acts and the General Board of Health led by Edwin Chadwick, a firm miasmatist. By this time, Dr Snow's anaesthetic work had probably made him more knowledgeable of the properties of gas and air than many miasmatists. He made a name for himself by having Queen Victoria as an anaesthesia patient.

The year also saw cholera arrive in London - a disease that the new acts were relatively powerless to stop. Though the leading scientific and medical communities of 1848 had little more to offer in fighting cholera, they were better prepared than before - many doctors had cholera experience, resulting in fewer arguments over diagnosis, local registrars were better established to record and communicate precise cause-of-death statistics and rail networks enabled faster communication.

In 1849, Dr Snow published his investigations from 1848 and before in the first edition of On the mode and communication of cholera. The book was widely rejected by the medical establishment (Snow Society, 2004). The London Medical Gazette (cited in Snow Society, 2004) reported that: "There is, in our view, an entire failure of proof that the occurrence of any one case could be clearly and unambiguously assigned to water." The reviewer later concludes that: "Notwithstanding our opinion that Dr Snow has failed in proving that cholera is communicated in the mode in which he supposes it to be, he deserves the thanks of the profession for endeavouring to solve the mystery. It is only by close analysis of facts and the publication of new views, that we can hope to arrive at the truth."

The index case in the Soho outbreak on 29 August 1854 at 40 Broad Street was a five-month-old baby with summer diarrhoea, reported to Dr Snow by Rev Henry Whitehead, who discovered that the baby's mother had flushed its slops into a sink connected to a cesspool near the Broad Street pump. Reading Dr Snow's second edition of On the mode and communication of Cholera (1855), one is often struck by the detail of his social observations derived from his exhaustive personal enquiries into the water supply and the other circumstances of the 600 cholera victims of the 1854 outbreak.

The popular Broad Street pump had a reputation for sweet tasting water and was used widely by coffee shops, publicans and in sherbet. Dr Snow's initial observations of the pump water found no physical impurities, but he had the foresight to leave it for two days, during which time "small, white, flocculent particles" developed. Further local enquiries revealed that, at the time of the outbreak, the pump water, though appearing clear and fresh, had an offensive smell.

Dr Snow's previous experiences also led him to investigate the wider Broad Street outbreak anomalies. His enquiries included the Poland Street workhouse where only five cholera deaths occurred among the 500 vulnerable workers. The workhouse relied on two more protected water sources and never used the Broad Street pump. Another interesting case in Hampstead was a wealthy widow who died of cholera on 2 September 1854. Her Islington niece also died of cholera, but district records revealed no other cases in either area. Later, Dr Snow discovered that each day the widow had sent for a cart from Broad Street to Hampstead, delivering a large bottle of pump water.

Arguably, Dr Snow's greatest epidemiological achievements were his two great experiments of 1854 - comparing cholera deaths in the districts supplied by the Southwark & Vauxhall Water Company with those of the Lambeth Water Company. In response to widespread pressure for purer water, the Lambeth company relocated its main abstraction point to Thames Ditton. Southwark & Vauxhall still abstracted water from the sewage-laden Thames at Battersea Fields. Using case information from Dr William Farr, Dr Snow divided the populations of these districts by water company, using a silver nitrate test to identify Vauxhall water on account of its high salt content. In 1855, he reported death rates of 153 per 10,000 population in houses supplied by Southwark & Vauxhall, compared with 26 per 10,000 population in houses supplied by the Lambeth company.

Dr Snow's second edition also included maps of his experiments and the Broad Street epidemic. Some controversy surrounds these, with a number of historians considering it more likely that Dr Snow used them for illustrative, not investigative, purposes. This is not to undermine his achievements, for historians believe that, while he undoubtedly thought geographically, his deduction of the Broad Street source was based on his previous study of similar cholera outbreaks, and not his induction from the geographical facts of the Soho epidemic.

In the end, Dr John Snow beat fellow scientist William Budd to the water theory of cholera transmission by 10 days. Though Budd's thesis was based on more thorough surveys of rural outbreaks, he proposed a fungal cause (Snow Society, 2004). The back of the Austin Reed shop in Regent Street marks the site of Dr Snow's last home - 18 Sackville Street, where he resided from 1853 until his death, aged 45 years, on 16 June 1858.

Back to 2004, at the twelth pump handle lecture, Dr Alain Moren, coordinator of the European programme for intervention epidemiological training (www.epiet.org), called on us to learn from Dr Snow's example. Describing current challenges for field epidemiology in a widening Europe, he pleaded for more free-thinking radicals like Dr Snow today - practitioners prepared to challenge accepted knowledge, to carry out comprehensive field investigations, to research and communicate their findings and intervene. Dr Moren used the Sars outbreak in Amoy Gardens - a series of residential tower blocks in Hong Kong - to illustrate his plea. Here, one popular theory of an aerosol spread through bathroom ventilation is now being reviewed following a more critical analysis of the outbreak. He concluded that the formation of the European Centre for Disease Prevention and Control in Stockholm in 2005 presented a great opportunity for us all to work together in the prevention and control of disease.

For more on Dr Snow's remarkable life and work, visit Prof Ralph Frerich's comprehensive website at www.ph.ucla.edu/epi/snow.html

Rob Couch is a member of the John Snow Society and a lecturer in environmental health at Middlesex University. The society promotes the life and works of John Snow to encourage communication and collaboration between specialists of the many disciplines that have benefited from Dr Snow's work. For more information, visit www.johnsnowsociety.org or contact Hannah Gregory by e-mail: johnsnowsociety@riph.org.uk