Dr. John Snow and the London Cholera outbreak

John Snow (1813-1858) was a British physician.

He is considered to be one of the fathers of epidemiology, because of his work in tracing the source of a cholera outbreak in Soho, England, in 1854.

We know cholera is caused by a bacterium (Vibrio cholerae).Symptoms include chronic diarrhoea, low blood pressure and dehydration.Infected patients can die within 3 hours if left untreated.

In 1854, there was a cholera outbreak in Soho, London.

It had devastating outcomes with over 500 fatalities.

Nearly all families lost at least one member (regardless of socioeconomic class).

People thought that cholera was caused by ‘bad’ air

John Snow did not believe this and he began to collect evidence

John Snow mapped where the cholera cases occured

By talking to local residents, Snow identified the source of the outbreak as the public water pump on Broad Street.

Snow later used a spot map to illustrate how cases of cholera were centred around the pump.

Snow concluded that all the people infected with cholera had drunk water collected from the Broad Street well.

It was later discovered that a leaking cess pit containing sewage was only 3ft away from the well and was contaminating the water.

Snow's studies of the pattern of the disease were convincing enough to persuade the local council to disable the well pump by removing its handle.

This caused the number of cholera cases to decrease rapidly.