Cholera is a highly infectious disease which kills its victims through dehydration. Its main symptoms are severe diarrhoea, vomiting and stomach pain; a sufferer can lose many litres of fluid a day. It is known as a disease of poor sanitation. During the first half of the nineteenth century, London was an extremely unhealthy place to live (see bookmark to Page 356, " the open sewer of the Thames ") and cholera epidemics were frequent.
In 1854 the cholera outbreak around Broad Street, Soho, led to over 500 deaths, but resulted in a breakthrough in the understanding of the spread of the disease. Dr John Snow traced the source of the outbreak to the Broad Street pump. Although he could not explain exactly why the pump was to blame, he persuaded the authorities to disable it, preventing the further spread of the disease. It was later discovered that the pump had been dug only three feet from a cesspit which was leaking contaminated water. A memorial pump stands on Broad Street, now called Broadwick Street, in honour of John Snow's discovery.