What lessons can middle school students gain from learning about the 1854 London cholera outbreak and John Snow’s Ghost Map? At a recent morning meeting, I told this story not only because I find it a fascinating anecdote that represents a seminal moment in the history of public health, but it’s also an exciting detective story. Beyond the titillating or gross factor of learning about cholera and the way it sickens and kills, I hope the students took away some important lessons about the way we do research and the interrelationship among disciplines.
The story of how Dr. John Snow came to be regarded as one of the pioneers in the field of public health is well known in many circles today. A highly-regarded physician and anesthetist, who had given chloroform to Queen Elizabeth to ease her labor pains, Snow became intrigued with the causes of the 1854 cholera outbreak. He refused to believe in the prevailing theory that it was a miasma, polluted gases, causing the disease, so he proceeded to study the incidence of cases to see if there could be another explanation for the epidemic. By mapping individual cases, which became known as his “Ghost Map,” he noticed a geographic clustering around a water pump in a certain section of London. The more he studied the data, the more he thought that there might be a connection between the water coming from the pump and the people becoming ill.
Unfortunately, Snow also faced the vexing conundrum of what to do with the cases that contradicted his evolving thesis. For example, how to explain the monks who lived near the pump but seemed immune to the disease or the cases of two cholera-infected individuals who lived miles from the pump? As with any of us who are confronted with contradictory data, Snow faced the frustration of either giving up on his theory or ignoring what his findings told him.
Like an earlier version of Sherlock Holmes, Snow pursued his investigation. In speaking with the monks, he learned that they drank beer rather than the water from the pump, so they avoided the bacteria. However, how could he explain the two anomalous cases that occurred further away? Snow went to the house of one of the women, Mrs. Eley, who lived miles away but had died from the cholera outbreak. It was only through a conversation with the recently deceased woman’s son that Snow learned that the woman in question had grown up near the Broad Street pump and enjoyed the taste of that particular water so much that she daily sent her servant for it. In addition, before she died, Mrs. Eley had been visited by a cousin who also lived far from the pump. Mrs. Eley had served her cousin a glass of water, and she passed away as well. Voila! The two women who initially seemed to disprove Snow’s theory, in fact, validated it. Ultimately, and to the benefit of later public health researchers, Snow’s research was one of the major steps in the development of germ theory.
As with any presentation I make to the students, I concluded with the question of what we can take away from this story. First of all, I hope that students learn not to accept a popular “theory of the day” as unquestioned gospel that cannot be revised. Secondarily, students should realize that the lines between disciplines are permeable and that science, geography, and math are truly interrelated. In addition, our students should focus on the constants in front of them, isolate the variables, and doggedly pursue the data, even when it may contradict their hypothesis. Not all of our students may be a modern day John Snow, Hercule Poirot, or Miss Marple, but they can all engage in the thrill of discovery and be detectives in their own right.
