The Ghost Map

Last year I heard Steven Johnson, author of The Ghost Map, interviewed on NPR's Science Friday. His book talks about the London cholera epidemic in 1854, and John Snow's famous epidemiology study to find the cause. This is a story that I've read about- it's in all the microbiology textbooks, and I tell it to my students each year. So, of course I was interested in learning more details about how it all occurred. I asked the library to order it, they did, and I am happy to report that I'm not at all disappointed!

The Ghost Map goes into great detail about the conditions of London of 1854- in particular the casual way that sewage was disposed of and treated (or not treated). Johnson sets the stage for the cholera outbreak and helps us to understand how easily the Broad Street well was contaminated with Vibrio cholerae, the bacteria that causes the disease. The players in the drama are described- including the background of John Snow and Henry Whitehead, two of the principle investigators of the outbreak.

There were a number of things in this book that I thought were especially interesting. One was a discussion of the effects of urbanization. Johnson describes how the shift from rural to urban plays a role in the control of disease. He has a tendency to wax poetic, talking about cities as growing, living organisms, but I think that it is a valid analogy. As people congregate, the way that wasted is eliminated and provisions for clean water all become major concerns.

At the time of the epidemic, the general thought was that disease was caused by miasma, the general "bad air" that would linger in certain neighborhoods. The Ghost Map talks about Snow's idea that contaminated water was the primary source. Snow goes to great length to gather information to back up his theory and convince the city health officials to remove the handle from the Broad Street pump, and thus end the outbreak. He eventually is able to, primarily because the health officials can't seem to find any other alternatives and have to do something- anything- to get things under control. It's interesting, however, to see that the "miasma" theory continues to linger, and it isn't until years later that Snow's theory begins to be widely accepted. I'm constantly reminded that we have certain ways of thinking about things, and it is very difficult to change our paradigm and accept groundbreaking new ideas. It makes me wonder what sorts of things we're missing out on these days! The author describes a number of studies that were done at the time that the miasmatists used as evidence for their theory, and discusses the difference between correllation and cause- communities with bad smelling air WERE the most likely to have outbreaks of disease, but that was a correlation, not a cause. People could look at other factors such as elevation, population, etc., and find similar correlations, which might bring them to believe that disease could be caused by poverty, crowded buildings.... the list goes on and on.

I thought The Ghost Map was well researched and the science itself was described in a pretty clear manner. One passage I particularly liked was the description of fermentation, a process which I try to teach about in a number of different classes, and never comes off quite as clearly as this:

Ironically, the antibacterial properties of beer- and all fermented spirits- originate in the labor of other microbes, thanks to the ancient metabolic strategy of fermentation. Fermenting organisms, like the unicellular yeast fungus used in brewing beer, survive by converting sugars and carbohydrates into ATP, the energy currency of all life. But the process is not entirely clean. In breaking down the molecules, the yeast cells discharge two waste products- carbon dioxide and ethanol. One provides the fizz, the other the buzz. And so in battling the health crisis posed by faulty waste-recycling in human settlements, the proto-farmers unknowingly stumbled across the strategy of consuming the microscopic waste products generated by the fermenters. They drank the waste discharged by yeasts so that they could drink their own waste without dying in mass numbers. They weren't aware of it, of course, but in effect they had domesticated one microbial life-form in order to counter the threat posed by other microbes. The strategy persisted for millennia, as the world's civilizations discovered beer, then wine, then spirits- until tea and coffee arrived to offer comparable protection against disease without employing the services of fermenting microbes.

All in all, I thoroughly enjoyed this book. It was a nice combination of history, science, and sociology, and now I'm excited for next year when I can share the rest of the story with my students. It also makes me eternally grateful to live when and where I do- with an abundance of clean water.