John Snow revisited

From another student in the Intro to GIS course.

Isn’t it strange how everything seems to go full circle? Arguably John Snow’s work using maps to figure out the source of the 1854 Broad Street cholera outbreak in London was the birth of using spatial analysis/maps for anything but figuring out where you are going. Actually, for much of history, maps weren’t even used for navigation by Europeans, the focus only shifting from the sky to the earth in the 1500’s (there is an interesting podcast on this, as well as some pretty obscure, but nonetheless highly interesting alternative uses for the mapping process). But despite this late start to mapping, humans have come incredibly far incredibly rapidly: from John Snow collecting cholera data by going door to door, and mapping by hand, to using Google Earth to predict where an existing outbreak might spread next, and now to predicting outbreaks before they even begin.

Rita Colwell and colleagues at the University of Maryland are working on using geospatial data from satellites to predict cholera outbreaks, even before they occur. This is based on preexisting satellite data on the temperature, height, and chlorophyll concentrations of seawater. The hope that soon satellites will also collect salinity and oxygen saturation, among other variables, which may help improve the model. It is known that as waters warm, phytoplankton flourish, and this is associated with increased outbreaks of cholera. But just how great of a correlation, and how predictions could be bettered, is where GIS comes into play. Colwell correlated the satellite data to cholera case statistics, with the hope of developing a model strong enough to predict up to six weeks of the future.

But as advanced as we may have become, in collecting and projecting data, we still face many of the same problems as John Snow did all those years ago. Back in the days of John Snow, there was no agency collecting outbreak locations, let alone the Internet on which to post them. But despite the fact that we are lucky enough to have such services available to us via the Internet, even if not physically going door to door, researchers have to write letters and emails in order to track down people. And of course there is the always the problem of data integrity: how much can we trust the data from a government disease agency? At least John Snow was collecting the data himself, and thus could trust it as much as he could trust humans to answer faithfully. So it is quite odd how both one of the earliest and one of the latest applications of GIS involves mapping cholera outbreaks, one looking backwards, one looking forwards, and yet we face many of the same problems.

It’s the circle of GIS life.

One Response to “John Snow revisited”

  1. totunroz says:

    The progress is undeniable though, even if we still have a hard time with some aspects, such as tracking down the cases. Let’s not forget that at John Snow’s time, they didn’t even know what was killing them or how was it spread, so the impact reflected by the number of deaths was tremendous. Now we know what causes it, when it might occur, where it might occur and probably how hard it will hit in terms of treatment cost and number of people affected. So I wouldn’t say we’ve come full circle, but see this as an evolving spiral. We’re definitely improving even though there are still shortcomings.