The Broad Street Pump Cholera Outbreak
By September 3, 127 people had died, and many of the residents panicked and fled the city. By September 7, almost 500 people were dead, and three-quarters of Soho’s residents had left. Snow lived close to Soho and began his investigation. He started by examining the neighborhood and spoke to as many of the remaining residents as he could. His goal was to find some kind of link and believed that water contamination was the key, but he couldn’t find the proof he needed.
He checked the water and was unable to find organic matter on it; a finding that seemed to discount the Miasma Theory. After interviewing the families of victims, Snow discovered that almost every one of them lived close to the water pump on Broad Street. On the Soho streets that were closer to another water pump, the number of fatalities was significantly lower. In fact, only 10 cases occurred in people that lived near another pump. In five of those cases, the victim used the Broad Street Pump and three others were kids who went to school near the pump.
The Map That Changed the World
By now, Snow was convinced that the Broad Street Pump was the cause of the epidemic and he created a map to prove it. On his map, Snow drew the area of Soho, and each death was represented by a bar. Upon the completion of his map, it was clear that the vast majority of cases were centered around the pump on Broad Street.
But that wasn’t all; as well as tracking those that lived near the pump, Snow tracked hundreds of cases of the disease to schools, pubs, businesses, and restaurants in the area. Snow kept meticulous records of his findings which are fascinating. For example, he spoke to someone who worked in a coffee shop and served customers glasses of water taken from the pump on Broad Street along with meals. She knew of nine customers who had cholera.
There was a bubbly drink called ‘sherbet’ which was extremely popular at the time. Snow found out that the powder was sometimes mixed with water from the pump and he believed it was the source of dozens of cases.
Even in instances where Snow was originally perplexed, he was ultimately able to find the answer. For example, he was puzzled by the deaths of two women who lived a long way from Soho. He finally made the connection after speaking to the son of one of the deceased. As it transpired, she used to live on Broad Street and liked the taste of water so much that she had it bottled and sent to her.
As important as it was to find out more about the victims, Snow also needed information about people who had escaped illness. He found the answer in the unlikeliest of places.