The Ghost Map Themes

The central theme of Steven Berlin Johnson’s The Ghost Map is illness—in particular, the Vibrio cholera bacterium, or cholera, which killed hundreds of thousands of Europeans throughout the 19th century. In Victorian London, where most of the book takes place, millions of people lived within a few miles of one another—a scenario that was as unusual at the time as it is ordinary in the 21st century. London, with its unprecedented population density, was a…

During the cholera epidemics of the 19th century, there were many scientists who tried to understand the precise causes of the disease. One of these scientists, John Snow, was particularly influential in the history of epidemiology (the study of how diseases spread). Snow was a model scientist, combining exhaustive, hands-on research with conceptual rigor to produce a strong, testable theory of the causes of cholera. However, Snow faced many challenges in studying cholera. Unlike…

The cholera epidemics of 19th century London inflamed prejudice in the city. Cholera kills indiscriminately—all things held equal, people of all races, genders, or social classes are equally likely to die of the disease. However, due to the squalid conditions of Victorian London, the working classes were far more likely to contract cholera and die than were upper-class Londoners, who lived in more spacious neighborhoods where diseases spread more slowly, had access to cleaner water…