Is Molecular Epidemiology a Germ Theory for the End of the Twentieth Century?

A recent article in this journal by Vandenbroucke drew a parallel between the possible intellectual fate of some current ideas in epidemiology and the last century's miasma theory of epidemics. Like some nineteenth century investigators, many contemporary epidemiologists are indeed guided by the principle that the origins of disease are environmental in a very broad sense. This is sometimes called the 'black box' view of epidemiology, and it emphasizes the documentation of exposure-disease associations in conjunction with the idea that disease can be prevented by altering the environment without the need of detailed knowledge of pathogenic mechanisms. Vandenbroucke's thesis is that epidemiologists who subscribe to this view, like the miasmists, their philosophical predecessors, are destined to be the losers in a struggle with a superior scientific idea. For the miasmists that competing idea was the germ theory of disease; for the epidemiologists of today, in his view, it is molecular biology. Such exhortations that epidemiology must alter its philosophy and methods to survive as a legitimate scientific discipline are not unusual but they are often based on a distorted view of the history and goals of epidemiology. This view is derived from a misinterpretation of the last century's intellectual contest between theories about the origins of mass disease. The conventional wisdom of today is that those nineteenth-century epidemiologists who subscribed to the theory that epidemics are completely explainable by the presence of specific agents in all affected populations won that contest because they were right, that is, because such agents are, by definition, the unique causes of disease. The virtue of their ideas is suppos-