Cholera and Epidemiology

November 15, 2007 12:49 PM

Sick City - Maps and Mortality in the Time of Cholera [print version] reviews Stephen Johnson's "The Ghost Map: The Story of London's Most Terrifying Epidemic"*. Dr John Snow became the acknowledged modern father of epidemiology by identifying water as the transmission vehicle of a cholera outbreak in Victorian England.

UCLA have an amazingly comprehensive website devoted to Dr John Snow (and much more) - worthy of a look if only for the nice maps.

posted by peacay (10 comments total)

The Ghost Map is an excellent book, though it turns out most of the things I thought I new about Dr Snow and his map were wrong - though he advanced the science of epidemiology he may not have had much impact on that particular outbreak, and the particular map I thought was the important one isn't.

I read it alongside A History of The WOrld In Six Glasses, which is also good and has some overlap with it.
posted by Artw at 12:56 PM on November 15, 2007

Iraq in the time of cholera
posted by Artw at 1:04 PM on November 15, 2007

damn i was just thinking about this guy while i was reading up on sewerage at work.
posted by camdan at 2:22 PM on November 15, 2007

I hate to sound like a grouch, but when there's an article about maps and cartography and it's in a popular magazine or newspaper, they always manage to muck it up by omitting the maps or publishing postage-stamp versions. As a map aficionado, that kind of thing always grates on me.
posted by chef_boyardee at 3:29 PM on November 15, 2007

we've got a big cholera outbreak in Vietnam at the moment. It's rather bizarre as I've always classed cholera as one of those diseases that happen in horrible places, elsewhere.
The vehicle so far remains unknown, but shrimp paste and herbs have been posited as possible candidates. Of course, I'd like to know what water they were using on those products.
posted by grubby at 6:40 PM on November 15, 2007

Ah, good old John Snow-- you can't be a student of public health without having his story drilled into your head. And not without good reason: Snow really was a genius, and a remarkably prescient one, and On the Mode of Communication of Cholelra still makes for good epidemiological reading today. But Snow has been turned into a tidy, instructive little fable, and everybody always tells it the same way.

I remember reading the New Yorker article when it was published, and being dissapointed by it (I can't speak for The Ghost Map, because I haven't read it). It made the classic mistake of claiming that John Snow removing the handle of the Broad Street pump ended the epidemic, which it did not, the epidemic being already pretty much over by that time. Snow admits as much in On Cholera, and it's a commonly pointed out misconception.

More importantly, the whole Broad Street incident is just a particularly large, well-documented, and well-illustrated version of the many stories in On Cholera. Snow presents numerous case studies that track the progression of the disease through water and other contagions in towns throughout England. He spends a lot of time looking at the behavior of cholera and discussing explanations for how and why certain phenomena tend to come up. Why do women get sick more often than men? Is it because they tend to the ill in the family? Because they wash the soiled bedding of cholera victims? Why do workers in brewhouses not get ill? Is it because they drink beer more often than water?

Snow also conducts what is, in both his and my opinions, a far more telling survey involving the water companies supplying London during the epidemics. At the time, there was little regulation of the companies bringing piped water into the city, and different firms used vastly different degrees of filtration and sedementation of the water. Finding neighborhoods where pipes from two companies ran parallel, where residents could chose to get water from one or the other, Snow recognized the opportunity for a wonderful natural experiment. He went door to door gathering data on death rates and water supplies, ultimately finding that the rate of cholera death in houses supplied by Lambeth was 5 per 10,000, while in those supplied by Southwark and Vauxhall, it was 71 per 10,000. Unlike the Broad Street case, no one could claim that the problem was the smell or the filth or the lose morals of the neighborhood; these were next door neighbors from a broad swath of town, with remarkably different death rates. This is the sort of stuff that epidemiologists do all the time today, but before Snow no one had ever really done it.

Which is the really amazing thing about all this: that no one was doing it. Contagion theory was in the air, and so was the theory of miasma, but no one on either side of the argument was approaching disease with as critical an eye as Snow. He is the father of epidemiology not just because he made that cool map (a later illustration of his discoveries, not in the original On Cholera, btw), but because he started people thinking about how diseases operate in the larger world, in populations instead of in individual bodies. He started us looking at how those larger phenomena could be observed and documented and, ultimately, stopped.
posted by bookish at 8:15 PM on November 15, 2007 [2 favorites]

Thanks very much for the elucidation bookish. If only I had imbued the post with as much eloquence, it might have generated a bit more interest.

The pump handle story may be a bit of an exaggeration (and in its defense, the New Yorker did say "Snow persuaded the parish Board of Guardians to remove the handle from the Broad Street pump, pretty much ending the Soho cholera outbreak.") but as far as embellished historical stories goes, it's at least not completely without foundation.

I think such poetic license can be given a bit of a free pass in the greater scheme (not for the tertiary scholars of course) because it operates as tangible anecdote by which the premise of water borne illness can be easily remembered by your average student, t'would think.

But yeah, I love the guy's logical questioning - that's, as you say, where his true genius lies. Critical thinking is an elegant art to behold.
posted by peacay at 9:43 PM on November 15, 2007

I have a framed copy of Mr. Snow's final map, there is more than one, in my office.

Data is God.
posted by ewkpates at 6:47 AM on November 16, 2007

Bookish - the book does indeed cover much of that, including thw misconceptions regarding the pump handle removal ending the outbreak.
posted by Artw at 9:12 AM on November 16, 2007

did anyone else think this article was VERY poorly written? like, so poorly written that it's kind of absurd that the new yorker published it in such a state?
posted by timory at 8:10 PM on November 16, 2007