The Ghost Map

Saturday, June 6, 2009 9:40 | Filed in Books, History, Reviews, Science

Steven Johnson writes about something I vaguely knew about — London’s Broad Street cholera outbreak of 1854. This is the story of how it was identified that cholera was somehow water-borne, as opposed to the previous beliefs that it was somehow carried by the smells or miasma of the urban filth.

The Ghost Map (amazon)

The commonly understood legend is that Dr. John Snow understood that the outbreak was clustered around a water pump near 40 Broad Street in London. Those using that water pump were much more likely to get cholera; those using a different pump still had a chance of catching it (as it wasn’t exactly uncommon), but much less. Dr. Snow explained this to various civic leaders, who removed the handle of the water pump and ended the outbreak.

And this is true, sort of. Only it misses out a lot of the detail, like the fact the civic leaders didn’t really believe in his water-borne contagion idea, but closed the pump because of the risk analysis — if they were wrong, shutting off the pump would save lives; if they were right, it would mean people would have to walk a few streets further for their water. It also misses out the point that it was a lot of follow up work after the outbreak which ultimately (but not for some years) established cholera as water-borne; and perhaps most strangely it suggests that the Broad Street pump was actually cholera-free at the time it was closed down, but that a second outbreak was prevented…

And all of this is what Steven Johnson’s book The Ghost Map explains. Firstly it tells the story of the urban conditions in London at the time (generally squalid and overcrowded), and of course how there was no form of sewer system. Instead, people just had cesspools and for hundreds of years, people had been paid to empty them:

The collecting of human excrement was a venerable occupation; in medieval times they were called “rakers” and “gong-fermors” [...] While the rakers and their descendants made a good wage, the work conditions could be deadly: in 1326, an ill-fated laborer by the name of Richard the Raker fell into a cesspool and literally drowned in human shit.The Ghost Map, p8-9

The history of the 1854 Broad Street cholera outbreak is also explained: a particularly virulent form of cholera which could take the afflicted from no symptoms to dead within twelve hours, killing 127 residents of the area within three days.

The cholera outbreak is also traced back to its index case: a five month old baby girl. This was discovered later by the Reverend Henry Whitehead who initially had sent out to debunk Dr. Snow’s theory, but ended up becoming convinced of it himself, and ending up being responsible for collection of some of the evidence that would finally convince the vestry report on the water-borne nature of the epidemic (although the official report at the time believed no such thing). You have to bear in mind at this time, there wasn’t a germ/microbial theory of infection, which makes the ability to track this down even more astonishing.

Basically, some of the dirty cholera-infected nappies of this baby girl were dumped in a cesspool at the front of Broad Street.

The walls of the cesspool were lined with bricks that were so decayed that they could “be lifted from their beds with least force”. Two feet and eight inches from the outer edge of the brickwork lay the Broad Street well. At the time of the excavation, the water line in the well was eight feet below the cesspool. Between the cesspool and the well, York reported finding “swampy soil” saturated with human filthThe Ghost Map, p179

…although by the time the pump handle was removed, people were drinking the water without succumbing to infection, as since the baby’s death, no more cholera-infected material was being added and the bacterium might have been dying off in the well.

The “Ghost Map” of the title was a map produced by Dr. Snow to compare where the deaths occurred. It’s basically a simple map of the street layout, with all of the deaths marked against the properties with a black bar, with the water pumps also marked on. It shows a fairly obvious clustering around the Broad Street pump — but it was the exceptions (those nearby not infected, those further away who were) who provided some of the clinching detail.

The massive engineering project that was London’s sewer system is also described, as well as how, once complete (as opposed to “not quite complete when people thought it was” in 1866) it provided protection to Londoners who never suffered another serious outbreak once cholera contamination was kept out of the drinking water supply…

For me, though, the thing that sticks in the mind is that cesspool that leaked into the water supply; and the human tragedy of one family — the Lewis family of 40 Broad Street — who were ultimately responsible for the outbreak:

It is not known if Sarah Lewis ever learned that the final days she spent tending to her daughter had triggered the most devastating outbreak in the history of London. If so, the weight of the news must have been unbearable, because the outbreak she had unwittingly set in motion eventually killed her husband as well. Thomas Lewis had fallen ill that Friday, within hours of the pump handle’s removal. He fought the disease for much longer than most, surviving for eleven days.The Ghost Map, p187

…and this is where it was fortunate that the handle was removed from the well. Because some of Thomas Lewis’ cholera-infected waste was dumped in that same cesspool (of course, Sarah Lewis was certainly not to know this at the time — not having been interviewed until the outbreak was over), providing a fresh new supply of cholera into the well, and could potentially have triggered a second wave of cases, had the pump handle not been removed.

It’s a powerful work; it’s not always pleasant reading, but it is captivating. Steven Johnson has done an excellent job of bringing the 1854 Broad Street cholera outbreak to life, explaining why the urban conditions led to cholera outbreaks — and how they led to the cholera bacterium evolving to become more virulent, and bringing the main players — Dr. Snow and the Reverend Whitehead very much into focus.

Anyone with an interest in science, in history, in ‘detective mysteries’, in urbanisation, in living conditions, or in any combination of the above will find something for them in here. This is not a dry, dusty history, but one that springs vividly off the page, hopefully not bringing Vibrio cholerae with it. Well worth a read.

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