In this 1828 satirical cartoon, a woman drops her teacup in disgust when she sees that a magnified drop of water from the River Thames is teeming with nasty little creatures – “Hydras, and Gorgons, and Chimeras Dire,” in the illustrator’s words. The Thames, London’s main source of drinking water, was awash with sewage. And yet for much of the 19th century, most people believed that cholera was transmitted via miasma, or vapours emanating from rotting waste. In 1854, however, Dr. John Snow tried to show that the disease is water-borne by tracing an outbreak to a particular water pump. Although doctors and public officials were slow to accept the theory and it wasn’t until 1883 that Robert Koch identified the bacterium behind cholera, Dr. Snow was eventually proved right. In the process, he sired the modern discipline of epidemiology – the study of how diseases spread and can be controlled.
Written by Daniel Cossins
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