Epilogue
In this Epilogue to the John Snow Case, we examine the fate of Snow and his theory, the Broad Street Pump, and cholera itself.
What became of Snow and his theories?
Snow's research and intervention in the Broad Street outbreak were only a small part of his broader investigations of cholera, as described in the Prologue. Compelling as they are to modern readers who know the end of the story, Snow's exhaustive books, articles, and presentations immediately influenced the opinion of very few scientific or medical authorities of his day in England or in Europe. Snow's work, when it was read, was largely rejected as "untenable" and inconclusive. Those who did value Snow's work thought that contaminated water might predispose persons to cholera, but unlike Snow, they did not believe that it was a sufficient single cause. His now famous 1855 edition of On the Communication of Cholera had sold only 56 copies by the time Snow, a lifelong bachelor, died in 1858 at the age of 45 (Chave, 1958, p. 347).
Virtually all authorities continued to hold complex airborne miasma theories of cholera transmission for several more decades. Recognition and acceptance of Snow's work would gradually increase for the next several decades, until the more foundational work of Koch and Pasteur cleared the way for contagion theory and documented the existence and disease-causing abilities of the "animalcules" (bacteria) hypothesized by Snow and others.
Snow himself was not widely known in epidemiology or medicine until more than 75 years after his death, when epidemiologist Wade Hampton Frost republished Snow's work in Snow on Cholera in 1936. In short, Snow labored in public health for about ten years for no pay and in relative obscurity. He died unrecognized for having come very close to understanding the nature of cholera and its transmission.
What became of the Broad Street Pump?
Astounding as it seems to modern readers, so few people of influence accepted Snow's waterborne theory of cholera that within several weeks after the outbreak, the Broad Street pump was back in service (Chave, 1958).
Records show that throughout London, shallow street pumps like that in Broad Street continued to be used for more than twenty years, but their existence was increasingly fought by medical and sanitary reformers who warned of the danger they posed. Even when cholera was present, the pumps often remained in service. This editorial by two physicians from the Times of London dated 28 July 1866, written during the peak of the next major cholera epidemic, complains bitterly that the Broad Street pump and others like it should be closed. Apparently, by then, the waterborne theory was gaining some credibility in the medical community, but the St. James vestry and others with authority over the pumps had evidently remained unconvinced.
Three days later, a medical officer wrote to the vestry, pleading, "I dare not take the responsibility of remaining quiet while these pumps are open, and, at the risk of offending you by my pertinacity, I implore you to order the pumps to be shut." According to Chave (1958), this letter apparently had its desired effect, and there is no further reference anywhere to the Broad Street Pump, other than a statement from the 1880's that it had been covered.
Today the pump location is marked by a small red marker on the curb, and by a pub bearing the name of John Snow.
What became of cholera?
In the 20th Century, sanitary improvements have largely eliminated cholera from industrialized countries. Cholera remains endemic in many areas of the world, however. The seventh cholera pandemic that began in Indonesia in 1961 continues. After a Peruvian outbreak in 1991, Central and South America saw more than one million cases and eleven thousand deaths through 1995, and the disease also continues to produce significant morbidity and mortality in Africa and Asia.
For more information on cholera, explore the following sites:
The Cholera Situation in the Americas (Powerpoint Slideshow)
Centers for Disease Control Information on Cholera
World Health Organization Information on Cholera Prevention
Bibliography on John Snow
In Conclusion
John Snow's epidemiologic investigations and interventions illustrate many of the principles of public health described by Dr. Carl Shy in his essay, What is Public Health, which is part of the Introduction to the UNC School of Public Health core curriculum. We hope you have enjoyed hearing and reading about his tireless studies of the conditions affecting health at the population level, and his small but famous intervention. It is also instructive to remember that Snow worked and died in obscurity, that his work and guiding theoretical framework had been rejected by almost every medical and public health expert in his day, and that he labored without pay.
Each discipline and department at the UNC School of Public Health continues to teach its students the core principles and practices of public health described by Dr. Shy and illustrated by Dr. John Snow. We continue to make progress in the United States and globally, but face many challenges as we try to understand and intervene effectively at the population level to improve health.
Thank you for completing the John Snow Case Study.