Source: BMJ 332, 1220, May 20, 2006.


The Medical Detective: John Snow and the Mystery of Cholera

Sandra Hempel, Granta Books, London. 2006, ISBN-13: 978-1-86207-842-0

Also issued in the United States as:

The Strange Case of the Broad Street Pump: John Snow and the Mystery of Cholera.

Sandra Hempel, University of California Press, January 15, 2007, ISBN: 0520250494

John Snow is perhaps the only doctor ever to be considered the founder of two medical disciplines: epidemiology and anaesthesiology. An early believer in the theory of contagion, he grasped the opportunity of a peculiarity in the water supply in London to gather quantitative evidence supporting his theory that cholera was transmitted by polluted water. 

In 1853-4, when a cholera pandemic hit London, one of the two major water supply firms, the Lambeth Company, had moved its Thames intakes upriver, above the tidal (and therefore sewage) reach. Snow showed that most of the cholera deaths occurred among clients of the other major water provider, the Southwark and Vauxhall Company, which still pumped its water in a polluted area of the Thames in the heart of London. We know a great deal about Snow's large scientific heritage because he was a prolific writer. But very little written testimony exists about his personal life and psychology beyond an expanded obituary.

Given the limited biographical material available, it seems that everything that might be written about Snow has already been said by other authors, or collected by Frerichs on a website devoted to Snow ( Indeed, Snow's fans will not learn anything new about him in The Medical Detective. Still, Sandra Hempel has succeeded in drawing a three-dimensional portrait of Snow by abundantly describing the place, time, and society in which he lived.

The Medical Detective reads like a well informed novel featuring Chadwick and Dickens, Queen Victoria and Florence Nightingale, and digressions on the history of Victorian medicine, of ether and chloroform, and of cholera. A mythical image of Snow as a brilliant doctor with a penetrating intuition about the cause of cholera and who ingeniously found a way to test it emerges. However, in contributing to Snow's mythology, Hempel fails to address some basic questions any detective would ask. Why Snow? Why London? After all, many bright physicians in Europe and elsewhere were tracking the causes of cholera at the same time. Many shared his contagionist views. But Snow lived in an appropriate socio-political and scientific environment. He had the opportunity to team up with William Farr, medical registrar for England and Wales, whose offices collected death certificates and reported their aggregated numbers weekly.

A key figure of Victorian medicine, Farr played a crucial role in Snow's success, which is not appreciated as much as it should be by Hempel. In December 1853, the registrar general had first noticed that the districts partially supplied with the improved water from the Lambeth Company suffered much less than the other districts from cholera, although, previously, these same districts suffered about as much as those supplied entirely by the Southwark and Vauxhall Company. Farr provided Snow with the names and addresses of the dead and made Snow's demonstration possible. Farr did not share Snow's views on the role of polluted water, but he was instrumental in the success of Snow's endeavour.

Snow is already the hero of an excellent children's book (The Blue Death: The True Story of a Terrifying Epidemic. London: Hodder Children's Books, 2001). Hempel has now staged him as a brilliant detective and paved the road for a popular movie, which will finally let Snow enter the pantheon of great doctors.

Alfredo Morabia, professor of epidemiology

City University of New York, United States

click to return to the Books on Snow site