The Ghost Map

The Ghost Map: The Story of London's Most Terrifying Epidemic--and How It Changed Science, Cities, and the Modern World by Steven Johnson, Riverhead Books, 2006. 

Cholera

This book is a study of the outbreak of cholera in London in 1854. Cholera originated in the Ganges delta. Cholera arrived in Britain in 1832. The cholera patient can be saved by the infusion of large amounts of water and electrolytes. But they did not know that then. The bacterium that causes cholera was discovered independently, first by the Italian anatomist Filippo Pacini (1854) and later by Robert Koch (1883). Pacini’s discovery was ignored at the time he made it, because scientists stubbornly stuck to the miasmatic theory of disease, described below.

Miasma

At the time of the early and mid nineteenth century cholera epidemics in London, most doctors believed in the miasmatic theory of disease. In particular, they believed that cholera was transmitted through the air. Excrement and rotting flesh smell bad because of putrescine, cadaverine and hydrogen sulfide, which are the waste products of anaerobic bacteria. The scientific thinking of the time was apparently performed by the rhinencephalon.

Cesspools

Residents of London traditionally sent their sewage to cesspools in their basements. The cesspools were emptied by night soil scavengers. The smelly air emanating from these basement cesspools was blamed for the spread of disease according to the miasma theory. With the flush toilet and plumbing, the basement cesspools started overflowing. There was a law passed in London in 1848 to start dumping sewage into the Thames, which had previously been a very clean river.

John Snow

John Snow received his doctorate of medicine in 1844. Later, he became a member of the Member of Westminster Medical Society. John Snow published studies of the use of ether and chloroform as anesthetics for surgery. Because of his research on ether and chloroform, John Snow had knowledge of the diffusion of gases, and knew the dose-response curve for anesthetic gases. This knowledge enabled Snow to find the flaws in the miasmatic theory. Snow also knew that cholera infected the intestines, but not the lungs, so the causative agent was more likely to be ingested than inhaled. Snow’s investigations occurred before Louis Pasteur’s germ theory of disease. Snow had a working class background. Unlike the landed gentry, Snow did not believe that the poor were morally or biologically inferior, so he discounted economic class as a possible cause of the epidemic.

Epidemiology

William Farr published Weekly Returns, which recorded deaths from cholera. His statistics tracked the victims’ age, sex, elevation and water source. Farr provided the mortality data that Snow analyzed. The Reverend Henry Whitehead, an assistant curate at St. Luke’s church in Soho,  canvassed the neighborhood to gather evidence to disprove Snow’s theory. Looking at the evidence he gathered, Whitehead came around to support Snow’s water-borne theory, and the two became friends.

Broad Street Well

The Broad Street Well was a popular source of drinking water in the neighborhood. Even during the cholera epidemic, the well water remained unusually clear and free from unpleasant smells, so people thought it was safe to drink.

Henry Whitehead identified the index case. The index case of the cholera epidemic was a baby girl named Frances Lewis whose family dumped her bowel movements into a cesspool in the basement of their house. The city excavated the ground between the cesspool and the Broad Street Well and found the soil to be porous. The baby’s cholera bacteria percolated from the family cesspool into the well, causing the epidemic.

Waterborne Transmission of Cholera

In 1849 John Snow published an article explaining the waterborne transmission of cholera. The establishment dismissed Snow’s theory, because they believed that cholera was caused by air that smelled bad. But with time, and with help from William Farr and Henry Whitehead, Snow was eventually able to convert the scientific establishment and government officials to the waterborne theory. Subsequent improvements in public sanitation have made cholera a thing of the past in the developed world.