Some would argue Geospatial analysis didn't come into being until computers were available, I would argue otherwise. Note I'm not using the term GIS in this context, because it's too broad and ambiguous. John Snow is credited as the father of modern Epidemiology (not the Game of Thrones character), though arguably he is also the grandfather of geospatial analysis. In 1854 John Snow was investigating a cholera outbreak in Soho, London. To do this he plotted death locations on a map and discovered a trend, everything was near the broad street pump. At the time the widely help belief was the disease was transmitted via "foul air", John disagreed and thought it was due to contaminated water and his map helped him prove it. Today we still have John's original map and data; so why not replicate his study using more modern tools.

Here's Dr. Snow's original map, if you'd like to read more into his work go checkout this wikipedia article

All my work was done using QGIS. In this first map I generated Voronoi Polygons using the pump locations. For each polygon the pump will be the centroid and all the space inside will be closed to that particular pump. Next I did a point in polygon analysis to get the death counts for each polygon.

This is just a basic heat map, it's clear to see that the majority of the fatalities are around the broad street pump. Well the evidence appears to be rather incriminating, I think it's safe to remove the Broad Street pump's handle now.