Question

John Snow is considered to be the father of contemporary epidemiology because of his studies of cholera outbreaks in London in the mid-1800s. Answer the following questions.

a. What was the prevailing idea of what caused cholera? What made Snow question that idea?

b. Explain his “Grand Experiment”.

c. Explain his research into the 1854 Broad Street pump outbreak.

Answer 1

a. It was believed by the people that the cause of cholera is ‘bad air’ from rotting organic matter. Snow wasn’t convinced that the cholera is spreading through bad air because the patients that he had met were all having gastrointestinal problems not respiratory problems. So he thought that the disease is probably spreading through contaminated food and water.
b. Snow in his grand experiment gathered data related to cholera death in an area supplied with water by two water companies. The Lambeth water company supplied water collected upstream from where sewage was discharged. Whereas S&V company collects water downstream to sewage discharge. The death rate in the people supplied with S&V water was ten times the rate in the houses supplied by Lambeth. Snow published a paper in August 1849 entitled "On the Mode of Communication of Cholera" in this paper he proposed his theory that the mode of transmission of this diseases is contaminated water, but his theory did not get much attention.

c. In 1854, cholera broke out in the Broad Street area of London. Snow identified the source of the outbreak as a public water pump. He mapped the deaths and identified that all 197 victims of cholera death lived within walking distance of the pump. His findings convinced the local authorities to disable the pump and eventually the cases of cholera lowered down. Later it was found that the pump was contaminated with cholera from a nearby cesspit.