In 1854, the working class Soho district of London experienced a particularly virulent outbreak of cholera. The leading theory of the day was that cholera, and indeed most diseases, were caused by “miasma” or bad, stinky air. Not too bad of a guess. But some doctors noticed that for cholera (actually a waterborne bacteria) the infection patterns didn’t seem to support the miasma theory. Data collection on disease and mortality rates and characteristics was in its infancy; physician John Snow was looking for data that would prove his theory of waterborne cholera. He found it by mapping the cholera deaths and the victims’ nearest source of pump water. By doing so it became quite clear that using a single water source, the Broad Street pump, was the biggest factor correlated with contracting and dying of cholera.
Kind of a cool story about one of the first examples of modern data-driven analysis. Not many authorities believed Snow’s analysis; it took several years (and another outbreak) for him to be vindicated by history. I admire Snow’s dogged determination, his sticking to the observable facts, and looking at things in a different way than anyone had ever done before. The author mentioned Snow’s key to a bulletproof analysis: identify the trend, explain outliers (unexpected manifestations) and (equally important) explain the lack of expected manifestations.
Now, the history of this whole thing is cool and interesting. But I had some problems with “The Ghost Map.” For one thing, it is too long. It’s actually a quick read, but there seemed be a lot of beating the same drum over and over about Snow and others discovering the source of the Broad Street contagion. Then there is the book’s conclusion, where the author asserts that we should all move to cities, fund genetic research, and get rid of nuclear weapons. Huh? Some admirable goals, I suppose, but I didn’t quite make the author’s leap from 19th century epidemiology to these other topics. My impression was that he now had the reader’s attention and wished to promulgate his personal opinions from that soapbox. Kind of dubious; if he wanted to write on those other subjects then I think he should have stuck them in a different book.