1854 Broad Street cholera outbreak

Broadwick Street showing the John Snow memorial and public house. The memorial pump was removed due to new construction in March 2016. A plaque affixed to the public house reads, "The Red Granite kerbstone mark is the site of the historic BROAD STREET PUMP associated with Dr. John Snow's discovery in 1854 that cholera is conveyed by water."

The Broad Street cholera outbreak (or Golden Square outbreak) was a severe outbreak of cholera that occurred near Broad Street (now Broadwick Street) in the Soho district of London, England in 1854. This outbreak, which killed 616 people, is best known for the physician John Snow's study of its causes and his hypothesis that contaminated water, not air, spread cholera. This discovery came to influence public health and the construction of improved sanitation facilities beginning in the 19th century. Later, the term "focus of infection" would be used to describe places like the Broad Street pump in which conditions are good for transmission of an infection.

Background

In the mid-19th century, the Soho district of London had a serious problem with filth due to the large influx of people and a lack of proper sanitary services: the London sewer system had not reached Soho. Cowsheds, slaughter houses and grease boiling dens lined the streets and contributed animal droppings, rotting fluids and other contaminants to the primitive Soho sewer system. Many cellars had cesspools underneath their floorboards which formed from the sewers and filth seeping in from the outside. Since the cesspools were overrunning, the London government decided to dump the waste into the River Thames, contaminating the water supply. London had already suffered from a "series of debilitating cholera outbreaks" which included an outbreak in 1832 and 1849 which killed 14,137 people.

Competing Theories of Cholera

Preceding the 1854 Broad Street cholera outbreak there were two competing theories on the causes of cholera in the human body. The London medical community debated between miasma theory and germ theory as two possible causes for the persistent cholera outbreaks in the city. The cholera-causing gram negative bacterium Vibrio cholerae, would not be isolated until 1854, ironically the same year as the Broad Street cholera outbreak, and not publicized until 1883 by Robert Koch, a German physician and bacteriologist.

Miasma Theory:

Miasma theorists concluded that cholera was caused by disease causing particles in the air, or miasmata which arose from decaying organic matter or other other dirty organic sources. "Miasma" particles were considered to travel through the air and infect individuals and cause cholera. Dr. William Farr, the commissioner for the 1851 London census and a member of the General Register's Office concluded that miasma arose from the soil surrounding the River Thames. The soil surrounding the river contained decaying organic matter which contained miasmatic particles and were released into the London air. Miasma theorists believed in "cleansing and scouring, rather than through the purer scientific approach of microbiology". Dr. William Farr later agreed with John Snow's Germ Theory following Snow's publications.

Germ Theory:

In contrast to the Miasma theory, the Germ Theory behind the cause of cholera labeled the principle cause of cholera as a germ cell that had not yet been identified. John Snow theorized that this unknown germ would be transmitted from person to person by ingesting water. John Simon, a pathologist and the lead medical officer for London labeled John Snow's Germ Theory as "Peculiar".

Excerpt from John Simon:

"This doctrine is, that cholera propagates itself by a ‘morbid matter' which, passing from one patient in his evacuations, is accidentally swallowed by other persons as a pollution of food or water; that an increase of the swallowed germ of the disease takes place in the interior of the stomach and bowels, giving rise to the essential actions of cholera, as at first a local derangement; and that ‘the morbid matter of cholera having the property of reproducing its own kind must necessarily have some sort of structure, most likely that of a cell."

Even though Simon understood John Snows theory he called into question Germ theories relation to the cause of cholera.

Outbreak

On 31 August 1854, after several other outbreaks had occurred elsewhere in the city, a major outbreak of cholera reached Soho. John Snow, the physician who eventually linked the outbreak to contaminated water, later called it "the most terrible outbreak of cholera which ever occurred in this kingdom."

Over the next three days, 127 people on or near Broad Street died. In the next week, three quarters of the residents had fled the area. By 10 September, 500 people had died and the mortality rate was 12.8 percent in some parts of the city. By the end of the outbreak, 616 people had died.

Dr. Edwin Lankester's Evaluation

Dr. Edwin Lankester, a physician who was part of a local research conglomerate that studied the 1854 Broad Street Cholera Epidemic. In 1866 Dr. Lankester came to his conclusion that the pump itself was the cause of the Cholera outbreak. He agreed with John Snow, however his opinion, like Snow's, was not publicly supported. Lankester eventually was named the first medical officer of health for the St. James District in London. This was the same area where the pump was located. Lankester subsequently closed the pump due to his theory on the source of cholera in the area and infection rates dropped significantly.

Investigation by John Snow

Original map by John Snow showing the clusters of cholera cases in the London epidemic of 1854. The pump is located at the intersection of Broad Street and Cambridge Street (now Lexington Street).

Snow was sceptical of the then dominant miasma theory that diseases such as cholera or the Black Death were caused by pollution or a noxious form of "bad air". The germ theory was not established at this point (Louis Pasteur would not propose it until 1861), so Snow was unaware of the mechanism by which the disease was transmitted, but evidence led him to believe that it was not due to breathing foul air. Though Snow did not know the mechanism by which the disease was transmitted he hypothesized that cholera was indeed spread by agent in contaminated water. He first publicized his theory in 1849, in an essay titled "On the Mode of Communication of Cholera". In 1855 a second edition was published, with a much more elaborate investigation of the effect of the water supply in the 1854 Soho outbreak.

By talking to local residents (with the help of Reverend Henry Whitehead), he identified the source of the outbreak as the public water pump on Broad Street (now Broadwick Street). Although Snow's chemical and microscope examination of a sample of the Broad Street pump water did not conclusively prove its danger, his studies of the pattern of the disease persuaded the St James parish authorities to disable the well pump by removing its handle. Although this action has been popularly reported as ending the outbreak, the epidemic may have already been in rapid decline, as explained by Snow himself:

There is no doubt that the mortality was much diminished, as I said before, by the flight of the population, which commenced soon after the outbreak; but the attacks had so far diminished before the use of the water was stopped, that it is impossible to decide whether the well still contained the cholera poison in an active state, or whether, from some cause, the water had become free from it.

Snow later used a dot map to illustrate how cases of cholera were centred on the pump. He also used statistics to illustrate the connection between the quality of the source of water and cholera cases. Snow's efforts to connect the incidence of cholera with potential geographic sources centred on creating what is now known as a Voronoi diagram. He mapped the locations of individual water pumps and generated cells which represented all the points on his map which were closest to each pump. The section of Snow's map representing areas in the city where the closest available source of water was the Broad Street pump circumscribed most cases of cholera.

There was one significant anomaly – none of the workers in the nearby Broad Street brewery contracted cholera. They were given a daily allowance of beer, and did not consume water from the nearby well. The water used in the brewing process is boiled during mashing which kills cholera bacteria.

Snow also showed that the Southwark and Vauxhall Waterworks Company was taking water from sewage-polluted sections of the Thames and delivering it to homes with an increased incidence of cholera. Snow's study is part of the history of public health and health geography, and can be regarded as the founding event of epidemiology.

In Snow's own words:

On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the [Broad Street] pump. There were only ten deaths in houses situated decidedly nearer to another street-pump. In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad Street, as they preferred the water to that of the pumps which were nearer. In three other cases, the deceased were children who went to school near the pump in Broad Street...

With regard to the deaths occurring in the locality belonging to the pump, there were 61 instances in which I was informed that the deceased persons used to drink the pump water from Broad Street, either constantly or occasionally...

The result of the inquiry, then, is, that there has been no particular outbreak or prevalence of cholera in this part of London except among the persons who were in the habit of drinking the water of the above-mentioned pump well.

I had an interview with the Board of Guardians of St James's parish, on the evening of the 7th inst [September 7], and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day.

— John Snow, letter to the editor of the Medical Times and Gazette

It was discovered later that this public well had been dug only 3 feet (0.9 m) from an old cesspit that had begun to leak faecal bacteria. Nappies used by a baby who had contracted cholera from another source were washed into this cesspit, the opening of which was under a nearby house that had been rebuilt further away after a fire and a street widening. It was common at the time to have a cesspit under most homes. Most families tried to have their raw sewage collected and dumped in the Thames to prevent their cesspit from filling faster than the sewage could decompose into the soil.

After the cholera epidemic had subsided, government officials replaced the Broad Street pump handle. They had responded only to the urgent threat posed to the population, and afterwards they rejected Snow's theory. To accept his proposal would have meant indirectly accepting the oral-faecal method of transmission of disease, which was too unpleasant for most of the public to contemplate.

John Snow's Post Outbreak Evaluation

John's Snow's analysis of cholera and cholera outbreaks extended past the closure of the Broad Street Pump. John Snow concluded that cholera was indeed transmitted through and affected the alimentary canal within the human body. Cholera did not affect either the circulatory or the nervous system and there was no "poison in the blood...in the consecutive fever...the blood became poisoned from urea getting into the circulation". According to John Snow this "urea" would enter through Kidney Failure. (Acute Renal Failure is a complication of Cholera)

Therefore the fever itself would be caused by kidney failure, not by a poison already present in the subjects bloodstream. Popular medical practices such as bloodletting would therefore yield itself not effective in this case. John Snow also argued that Cholera was not a product of the Miasma theory. "There was nothing in the air to account for the spread of cholera". Cholera according to Snow was indeed spread by ingesting a substance, not through atmospheric transmittal. Snow cited that two sailors, one with cholera and one without, eventually both became sick from ingesting bodily fluids accidentally.

Involvement of Henry Whitehead

Rev. Henry Whitehead

The Reverend Henry Whitehead was an assistant curate at St. Luke's church in Soho during the 1854 cholera outbreak.

A former believer in the miasma theory of disease, Whitehead worked to disprove false theories, eventually focussing on John Snow's idea that cholera spreads through water contaminated by human waste. Snow's work, particularly his maps of the Soho area cholera victims, convinced Whitehead that the Broad Street pump was the source of the local infections. Whitehead then joined Snow in tracking the contamination to a faulty cesspool and the outbreak's index case.

Whitehead's work with Snow combined demographic study with scientific observation, setting an important precedent for epidemiology.

Board of Health

The Board of Health in London had several committees, of which the Committee for Scientific Inquiries was placed in charge of investigating the cholera outbreak. Their main focus was to be the atmospheric environment in London; however, they were also to examine samples of water from several water companies in London. The committee found that the most contaminated water supply came from the South London water companies, Southwark and Vauxhall.

As part of the Committee for Scientific Inquiries, Richard Dundas Thomson and Arthur Hill Hassall examined what Thomson referred to as "vibriones". Thomson examined the occurrence of vibriones in air samples from various cholera wards and Hassall observed vibriones in water samples. Neither identified vibriones as the cause of cholera.

As part of their investigation of the cholera epidemic, the Board of Health sent physicians to examine in detail the conditions of the Golden Square neighbourhood and its inhabitants. The Board of Health ultimately attributed the 1854 epidemic to miasma.

The Broadwick Street Pump Today

There is currently a replica pump where the original pump stands. The original location of the pump is marked by a red granite paver. Every year the John Snow society holds a ceremony where they remove and reattach the pump to pay tribute to John Snow's historic discovery.

See also

• Filippo Pacini
• Great Stink
• Joseph Bazalgette
• William Budd
• Epidemiology of tuberculosis
• The Ghost Map

External links

• Interactive version of John Snow's Map (Ghost Map)