Dr Hellis’ map of cholera in Rouen was published in his 1833 book. Its graphic novelty was in that the map plotted each cholera case as a red dot on a highly detailed map, allowing for the visual inspection of the relationship between the location of shipping crew and clusters of disease. Red lines were also used to outline establishments such as the prison or army barracks. The report also records the ports of origin of the ships, yet Hellis still read the clusters of disease by ship as being to do with the predisposition of the sailors (such as food consumed on the voyage), rather than their having been exposed and having spread the disease on the ship. However, despite this, his analysis of the map led him to observe that cholera dispersed along the banks of the river and into particularly impoverished and run-down dwellings, so starting, at least in principle, to favour a contagion theory.
Figure 1: Section of map of Cholera, Rouen, courtesy Emmanuel Elliot and the Geoconfluences project http://geoconfluences.ens-lyon.fr/informations-scientifiques/dossiers-thematiques/geographie-de-la-sante-espaces-et-societes
A recent study assessed the Hellis map with a cellular automata method for modelling the two main factors assumed to be responsible for propagating Cholera: the presence of an aquatic environment (river and wells) and the density and level of income (measured by charitable expenditure). The model found a close association between modelled health risk according to the social and spatial determinants and the clusters of high rates of cholera.[ii] The analysis provides evidence that places of exchange (such as markets), the quality of the housing, poverty and – importantly – water supply, were all likely to have contributed to the spread of the disease over and above the fact that its original source may have been seafarers coming into the city.
Figure 2: Density map of cholera cases. From “Cholera in the 19th Century: Constructing Epidemiological Risk with Complexity Methodologies.”
Cholera continued to be a matter of major concern throughout the nineteenth century, as the battle between the prevailing theory that it was transmitted through the air – the ‘miasma’ theory and those that believed it was transmitted through diseased water. In next week’s blog post we will move to London’s Soho to see the work of John Snow.
 Eugene-Clement Hellis, “Memories of Cholera in 1832” (in French). (Paris: Ballière, 1833), Source: Bibliothèque nationale de France, Department of Science and Technology, 8-TD57-389: http://catalogue.bnf.fr/ark:/12148/cb30589490z. Origin: National Library of France.
[ii] Éric Daudé, Emmanuel Eliot, and Emmanuel Bonnet, “Cholera in the 19th Century: Constructing Epidemiological Risk with Complexity Methodologies” (paper presented at the The 3rd International Conference on Complex Systems and Applications, 2008); see especially page 6.