Broadstreet Pump Cholera Epidemic of 1854

The Broad Street cholera outbreak was a severe outbreak of cholera that occurred near Broad Street (now renamed Broadwick Street) in the Soho district of London, England in 1854. Cholera leads to an infection of the small intestine which results in extreme diarrhea which may lead to massive dehydration and death. The disease can be treated by giving the victim a lot of fluids -- either by mouth or intravenously (directly into the blood stream).

John Snow was a respected scientist investigating the outbreak. Snow did not subscribe to the common belief that miasma (poisonous or bad air)
caused the disease. The germ theory (the belief that microorganisms were the cause of many diseases) was not widely accepted at this time, so he was unaware of the mechanism by which the disease was transmitted, but evidence led him to believe that it was not due to breathing foul air.

By talking to local residents (with the help of Reverend Henry Whitehead), Dr. Snow plotted the distribution of deaths on a map. He confirmed that an unusually high number of deaths were taking place near a water pump on Broad Street. He suspected the source of the outbreak as the public water, and not something in the air. Although Snow's chemical and microscope examination of a sample of the Broad Street pump water was not able to find anything suspicious, 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. This was done and the number of cholera deaths was dramatically reduced. This action has been commonly reported as ending the outbreak.

The work of Doctor Snow stands out as one of the most famous and earliest cases of geography and maps being utilized to understand the spread of a disease. Today, specially trained medical geographers and medical practitioners routinely use mapping and advanced technology to understand the diffusion and spread of diseases such as AIDS and cancer.

Activity Answer the following questions in complete sentences: What question was Snow trying to answer?  What did most people at that time think the cause was? Identify variables in Snow's study. (manipulated, responding, and controlled) Write a hypothesis statement using the Manipulated and Responding Variables. How was this a controlled experiment?