John Snow’s Ghost Map

Map recreating John Snow’s ‘Ghost Map’ of the Soho cholera epidemic of 1854.

The John Snow data of the Soho (a central district of London) cholera outbreak of 1854 is a classic study for those learning data visualisation. Snow is recognized as one of the founders of modern epidemiology (I learn that some also consider him the founder of data visualization, spatial analysis, and data science in general).

By creating his now famous ‘Ghost Map’ Snow saw the concentration of deaths around an epicentre, a single water pump situated on corner of Broad Street (now Broadwick Street) and Cambridge Street (now Lexington Street) which gave him import clues to as to the disease vector (a waterborn pathogen) as well as enabling him to advise the city authorities how to stop the outbreak (by removing the handle from the pump, as well as advising the boiling of water in the area).

Here in less than 20 lines of python code we can recreate Snow’s map from his data points: deaths (red), and pumps (blue). The nice black and white map is generated using the folium package. Credit to DataCamp for teaching me the techniques used here.