In 1854 there was a cholera epidemic in London.
The accepted theory at the time was that illness and epidemics spread through the “miasma”, a form of “bad air”, pollution and smell emanating from decomposing organic matter. The mechanics of germs was not understood.
Dr. John Snow was sceptical to the miasma theory, but not entirely grasping germ mechanics, he did this admirable thing: scientific observation, quantitative and qualitative data collection and using the best medium for studying the results.
He talked to the residents in the area of outbreak. He then hypothesised that there was a water pump that was the source. He took water samples, but these were inconclusive. He gathered data on how many people had died and where they lived. Plotting this on a map, it seems clear that infections are concentrated around the Broad Street water pump: 
However; there are inconsistencies that are a little problematic to explain, looking at the map. Armed with the quantitative data, our Dr. Snow did some more research by talking to people living at points where these oddities occur.
Quite a long way away from the Broad Street pump, closer to other pumps, some people got infected. The reasons, it turned out, being that children living there went to school closer to Broad Street, or that the people living there preferred the water from the Broad Street pump, considering it better.
Another anomaly was a few buildings close to the pump that had no infections, for example a a work house and a brewery. Some further researched showed that the work house had their own water source, and that brewery employees did not really drink water, they drank beer…
So, if there was ever uncertainty; graphics are beneficial for public health.
Matt Harris says:
what happened to Dr Snow? did he survive the outbreak?
boblet says:
He survived, became the father of modern epidemiology, and boiled all his drinking water for the rest of his life.
Trinity says:
Interesting article! I came across this story when I was researching for novels; the outcome of his research was that he presented it to the authorities; the next day the pump’s handle was removed, and the epidemic subsided. They later found out that the pump had been dug within a few feet of a former cesspit, which was seeping into the water… duh… but they didn’t understand bacterial cause and effect back then, so I suppose they’re excused (from killing hundreds…!).
boblet says:
Yes, that is right. It turns out that the epidemic was receding anyway, and the removal of the handle was not statistically the sole reason why the epidemic receded. But helping in removing the miasma theory, and the wonderful new research opened in epidemiology.
The thing is; it was hard to break traditions. The idea that doctors should wash their hands between handling cadavers and delivering babies, was not popular. Consider; admitting/realising that thousands of patients had died unnecessarily was a gigantic camel to swallow. Doctors were learned, knowledgeable, admired, and to admit that they effectively had killed patients for centuries simply by not washing their hands… well. There was a lot of resistance to the hypothesis of germs.
Miserable to think of, but fascinating history!
Trinity says:
Yep. Same thing with scurvy; ships’ barber-surgeons recognized the cause and how to treat it with the means at their disposal (lemon juice, fresh fruits and fresh water), but the big-wigs at the surgical college in London refused to be lectured by barbers, and so the information was slow to spread (and vehemently denied), resulting in thousands of unnecessary deaths…
boblet says:
Ohh, there you got me thinking about polar exploration, Amundsen, Nansen, Scott, and the interesting fact that the eskimos handle it by eating intestines of game and dogs…