This outbreak, which killed 616 people, is best known for the physician John Snow's study of its causes and his hypothesis that germ-contaminated water was the source of cholera, rather than particles in the air (referred to as "miasma").

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.

[3] Since the cesspools were overrunning, the London government decided to dump the waste into the River Thames, contaminating the water supply.

[7] Miasma theorists concluded that cholera was caused by particles in the air, or "miasmata", which arose from decomposing matter or other dirty organic sources.

[6] Dr William Farr, the commissioner for the 1851 London census and a member of the General Register's Office, believed that miasma arose from the soil surrounding the River Thames.

John Simon, a pathologist and London's lead medical officer, called Snow's germ theory "peculiar".

[6] 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.

According to a letter by Elizabeth Gaskell, Nightingale "was up night and day from Friday afternoon (Sept. 1) to Sunday afternoon, receiving the poor creatures (chiefly fallen women of that neighbourhood - they had it the worst) who were being constantly brought in - - undressing them - putting on turpentine stupes, et cetera, doing it herself to as many as she could manage".

Although Snow's chemical and microscope examination of a sample of the water from this Broad Street pump water did not conclusively prove its danger, the patterns of illness and death among residents in Soho persuaded the St James parish authorities to disable the pump by removing its handle.

[12] Although this action has been popularly reported as ending the outbreak, the epidemic may have already been in rapid decline, as explained by Snow: 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.

The section of Snow's map representing areas in the city where the closest available source of water was the Broad Street pump had the highest incidence of cholera.

Snow showed that the Southwark and Vauxhall Waterworks Company was taking water from sewage-polluted sections of the Thames and delivering it to homes, resulting in an increased incidence of cholera among its customers.

[19] 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.

The result of the inquiry then was, that there had 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.

[17] After the cholera epidemic subsided, government officials replaced the Broad Street pump handle.

Snow's work also led to a far greater health and safety impact than the removal of the Broad Street pump handle.

[23] Snow was sceptical of the prevailing miasma theory, which held that diseases such as cholera or the Black Death were caused by pollution or a noxious form of "bad air".

Both provided water to their customers drawn from the Thames, which was highly contaminated with visible and invisible products and bacteria.

Dr Hassall examined the filtered water and found it contained animal hair, among other foul substances.

Each company supplies both rich and poor, both large houses and small; there is no difference in the condition or occupation of the persons receiving the water of the different companies...As there is no difference whatever either in the houses or the people receiving the supply of the two Water Companies, or in any of the physical conditions with which they are surrounded, it is obvious that no experiment could have been devised which would more thoroughly test the effect of water supply on the progress of Cholera than this, which circumstances placed ready made before the observer.

He proved this by observing London prisons, finding that cholera ceased there only a few days after switching to cleaner water sources.

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 joined Snow in tracking the contamination to a faulty cesspool and the outbreak's index case (the baby with cholera).

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

[2] As part of its 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.

[2] Dr Edwin Lankester was a physician on the local research conglomerate that studied the 1854 Broad Street Cholera Epidemic.

Lankester eventually was named the first medical officer of health for St James's parish in London, the same area where the pump was located.