The 1854 Broad Street cholera outbreak was a severe outbreak of cholera that occurred near Broad Street (now renamed Broadwick Street) in Soho district of London, England in 1854. This outbreak is best known for John Snow's study of the outbreak and his discovery that cholera is spread by contaminated water.
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. Many cellars (basements) had cesspools of nightsoil underneath their floorboards. Since the cesspools were overrunning, the London government decided to dump the waste into the River Thames. This action contaminated the water supply, leading to the cholera outbreak.
On 31 August 1854, after several other outbreaks had already occurred elsewhere in the city, a major outbreak of cholera struck Soho. John Snow, the physician who linked the outbreak to contaminated water, later called it "the most terrible outbreak of cholera which ever occurred in the United 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.
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 was not able to conclusively prove its danger, his studies of the pattern of the disease were convincing enough to persuade the local council 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.