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Cholera in Porto Alegre

Cholera was carried to northern Brazil in May 1854, infecting many parts of the coast by the end of the year.  See an earlier post on its spread.  Several regions were struck the hardest, with mortality rates exceeding 10 percent.  One such place was the southern province of Rio Grande do Sul and its capital, Porto Alegre.  Municipal inspectors reported mortality rates from various parts of the city and these data were compiled by the Provincial Government and published as a set of tables.  We visualized mortality data by city blocks in the map above with red dots that represent parts of the city where cholera mortally rates were the highest, or with blue dots, where it was the lowest.  More precisely:

Red:  18-35 percent mortality
Light red: 13 – 17.9 percent mortality
Grey:  8.5 -12.9 percent mortality
Light blue: 5.5-8.4 percent mortality
Blue:  3.9-5.4 percent mortality  

Data were reported by quarteirões, or city blocks, which imperfectly aggregate dissimilar parts of the city.  Nonetheless, the pattern that emerges suggests that cholera killed more people living in the lower elevations closer to the water’s edge of Guaíba Lake, particularly on the northern end of the city.  The map below (which has been turned for visual alignment) gives some general contour lines.  By comparing these two maps, we can see that those living on higher ground, slaves and free, may have faced a somewhat smaller risk of this water born disease.  Elevation has been shown to be an important factor in recent cholera epidemics, according to a study of epidemic cholera in Harare, Zimbabwe.


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