Who made John Snow a hero?
This paper describes how and why John Snow's investigation of the transmission of cholera grew into an epidemiologic classic. The evolution of the interpretation of the work of John Snow was first studied in depth in the Dutch medical literature, and thereafter traced more superficially in the bacteriologic, hygienic, and epidemiologic literature of Germany, the United Kingdom, and the United States. From the oral tradition of teaching, as well as from the written sources, it is concluded that US epidemiologist W. H. Frost was responsible for the revival of the work of John Snow in the 1930s. Besides the obvious and enjoyable clarity of thinking and reasoning, epidemiologically and medically, of the writings of John Snow, his example well suited epidemiology of the 1930s since his convictions came very close to the bacteriologic paradigm of the day.