The Ghost Map

John Snow is, of course, well known as one of or maybe the founding father of public health. I have just finished Steven Johnson's book 'The Ghost Map' which reads like a detective story and describes the story of the cholera epidemic that hit Soho, London in 1854 (see a video with an interview with Steve Johnson about his book). The book gives a very lively account of what London must have been like in the years before and the time of the epidemic, and of the 'heroes' of the story, Dr. John Snow and Reverend Henry Whitehead in particular.
The story begins to descibe what led to the epidemic. The over-crowded inner city of London had become one big stink of human waste. The so-called cess pools meant to collect human waste, and supposed to be regularly emptied and the waste transported to fertilize the soil surrounding the big city, had become too few, too small, and just insufficient. Therefore, cellars and backyards in London city were filled with raw sewage; London was kind of drowning in its own filth. Johnson very nicely describes how a false theory of causation can lead to disastrous measures to promote public health that have the opposite effect. The miasma theory claimed that cholera was transmitted by air. The basic idea was that the stench from the enourmous collection of human waste was what caused cholera to spread. To contribute to rid the city of this presumed cause of cholera, infected air, London city passed the "Nuisance Removal and Contagious Disease Prevention Act" (Nuisane meaning human waste...) which resulted in using the existing London drainage system to transport human waste from the cess pools, cellars and back yards right into the river Thames; that is, the main source of drinking water for the city.
I think Steven Johnson's book is a very nice and entertaining must-read for people interested in epidemiology and public health. It describes the very start of our interesting field of research and practice. But, even more so, it illustrates what harm can come from bad or insufficient researched theories on public health risks, and how good research can help to set things straight.
Today we are faced with another serious public health problem with probable causes in how we have shaped our physical environment. The present-day obesity epidemic is likely to be partly rooted in what has been called the 'obesogenic environment', an environment that promotes eating energy-dense foods almost always and anywhere, and that discourages and prevents physical activity. However, convincing evidence on what really constitutes this obesogenic environment is mostly lacking. Snow's lesson so nicely described in Johnson's book is that we should be prudent in taking far fetching public health measures before we really know what we are doing. We should conduct the right research first. We aim to contribute to building the evidence-base in the Health promotion through Obesity Prevention across Europe project (HOPE).