Broad Street Cholera Outbreak (1854): John Snow and the Pump

The Broad Street cholera outbreak was a sudden and deadly epidemic in Soho, London, in late August and September 1854. Within ten days more than 500 people died, most of them living near a public water pump on Broad Street. The physician John Snow traced the deaths to the pump’s contaminated water and persuaded local officials to remove its handle, an episode now regarded as a founding moment of modern epidemiology, the study of how diseases spread in populations.

London and cholera

By 1854 cholera was a familiar terror in Britain. It had first arrived during the second cholera pandemic in 1831 and 1832, returning in 1848 and 1849 when tens of thousands died in England and Wales, including about 14,000 in London.

London was the largest city in the world, with more than two million people. Its water came from private companies, several of which drew it from the River Thames downstream of sewer outflows. Many households still relied on cesspools, and in poorer districts people drew water from public pumps fed by shallow wells.

Most doctors and officials believed in miasma theory, the idea that diseases such as cholera were caused by poisonous air rising from filth, rotting matter and sewage. The idea was powerful because foul smells and disease often went together. But it led reformers to flush waste into the Thames, which actually made the water supply worse.

Even careful statisticians accepted it. William Farr, the leading medical statistician at the General Register Office, analysed the 1848 to 1849 epidemic and found that cholera deaths fell as the height of a district above the Thames increased. He interpreted this as evidence that the dense, polluted air near the river carried the disease.

John Snow

John Snow, born in York in 1813, was a London physician and a pioneer of anaesthesia. He studied the effects of ether and chloroform and in 1853 gave chloroform to Queen Victoria during the birth of Prince Leopold.

Snow had long doubted the miasma theory. Because cholera attacked the gut first, he reasoned that it must be swallowed, not breathed. In 1849 he published a pamphlet, On the Mode of Communication of Cholera, arguing that the disease was spread by a poison passed in the evacuations of the sick and taken in through contaminated water or food. Few were convinced.

The outbreak

Cholera had been present in London during the summer of 1854, but on the night of 31 August an explosive outbreak began in Soho, a crowded district of workshops, small businesses and lodging houses in the parish of St James, Westminster. Within three days 127 people living around Broad Street had died. By 10 September the toll exceeded 500, and many surviving residents had fled.

Snow lived nearby and immediately suspected the much-used pump at the corner of Broad Street and Cambridge Street. He examined the water, which looked fairly clean to the naked eye, and obtained a list of deaths from William Farr at the General Register Office. Going from house to house, he found that nearly all of the deaths had occurred close to the pump, or among people who regularly drank its water.

On the evening of 7 September Snow presented his evidence to the Board of Guardians of St James’s parish. The board was sceptical, but agreed to act. On 8 September 1854 the handle of the Broad Street pump was removed, so that no more water could be drawn.

The number of new cases was already falling, partly because so many people had fled or died. Snow acknowledged this. Nonetheless, the removal of the handle became a powerful symbol of public health action based on evidence.

The evidence

Snow’s strongest arguments came from the exceptions. A workhouse on Poland Street with 535 inmates had its own well, and only five of its residents died. Around 70 workers at the Lion Brewery on Broad Street, who were given free beer and had a private well, escaped cholera entirely. At a percussion-cap factory at 37 Broad Street, where workers drank pump water from tubs kept on the premises, 18 died.

Snow also learned from Whitehead and other local informants that several people who had died lived closer to other pumps but preferred the Broad Street water, which was known for being cool and clear. Others had drunk it in local coffee shops and eating houses, or in sherbet drinks made with the pump water.

Most striking was the case of a widow living in Hampstead, far from Soho. She had once lived near Broad Street and liked the taste of the water so much that she had it carried to her daily. She died of cholera, as did a niece who visited her from Islington. No other cases occurred in those areas at the time.

Snow published his findings in the expanded second edition of On the Mode of Communication of Cholera in 1855, together with a map. On it, each death was marked by a small black bar at the address where it occurred. The bars clustered thickly around the Broad Street pump and thinned out near other pumps.

In the same book Snow also presented another study that he called the “Grand Experiment”. In south London, two companies supplied water to the same streets: the Southwark and Vauxhall Company, which took water from the Thames at Battersea, contaminated by sewage, and the Lambeth Company, which had moved its intake upstream to Thames Ditton in 1852.

Comparing the households supplied by each company during the 1854 epidemic, Snow found that homes supplied by Southwark and Vauxhall suffered about 315 cholera deaths per 10,000 houses, against about 37 for those supplied by Lambeth. Since the two groups were otherwise similar, the water was the obvious difference.

The index case

Not everyone was persuaded. The Reverend Henry Whitehead, curate of St Luke’s church on Berwick Street, set out to disprove Snow, believing the outbreak was a divine visitation or caused by bad air. His own detailed investigation instead confirmed Snow’s theory.

In 1855 Whitehead identified what was probably the first case: Frances Lewis, a five-month-old baby living at 40 Broad Street, who fell ill around 28 August and died on 2 September. Her mother had soaked the child’s soiled nappies in water and emptied it into a cesspool just a few feet from the pump’s well. When the well was excavated, the brickwork between the cesspool and the well was found to be decayed, allowing sewage to seep through.

Reaction and later recognition

A committee set up by the national General Board of Health rejected Snow’s explanation and continued to favour miasma. The parish’s own Cholera Inquiry Committee, on which Whitehead served, was more sympathetic and published a version of Snow’s map. Snow died in June 1858, aged 45, before his views were widely accepted.

That same summer the Great Stink of the Thames finally pushed Parliament to fund Joseph Bazalgette’s new sewer system, built for miasmatic reasons but with the effect of protecting the water supply. During the 1866 cholera outbreak in East London, William Farr, once a believer in miasma, traced deaths to a water company and accepted Snow’s view. In 1883 Robert Koch identified the cholera bacterium, Vibrio cholerae, which the Italian anatomist Filippo Pacini had described in 1854.

Myths and facts

A popular image shows Snow using his map to discover the source of the outbreak. In fact he identified the pump first, through enquiries and his existing theory. The map was drawn afterwards to illustrate and communicate his argument.

It is also often said that removing the handle ended the outbreak. The epidemic was already in decline, and it is impossible to know how much the removal itself saved lives. Its importance lies in the method behind it.

Today the site is marked in central London. Broad Street was renamed Broadwick Street in 1936, and a replica of the pump, without a handle, stands near the original location. The nearby pub was renamed the John Snow in his honour, and public health specialists still visit the spot.

By the numbers

Timeline

• 1849: Snow publishes the first edition of On the Mode of Communication of Cholera.
• 1854, 28 August: Baby Frances Lewis falls ill at 40 Broad Street.
• 1854, 31 August: The explosive outbreak begins in Soho.
• 1854, 7 September: Snow presents his evidence to the parish Board of Guardians.
• 1854, 8 September: The pump handle is removed.
• 1855: Snow publishes his expanded second edition with the map; Whitehead identifies the index case.
• 1858, 16 June: John Snow dies in London.
• 1866: Farr links an East London cholera outbreak to contaminated water.
• 1883: Robert Koch identifies the cholera bacterium.

Why it matters

The Broad Street outbreak showed that careful observation, mapping and statistics could reveal how a disease spreads, even before its cause could be seen under a microscope. John Snow’s work helped overturn miasma theory, encouraged clean water and sewerage, and created methods still used by epidemiologists today. Cities from London to Hamburg would learn, sometimes painfully, that safe drinking water is the foundation of public health.