The Evolution of Public Health Research: Snow’s Dilemma

Posted by Jaydeb Mukherjee on Feb 9, 2016 11:00:00 AM


Since the dawn of humanity, we have observed nature and hypothesized reasons behind how and why things happen. With the development of civilization, we standardized the methods with which we test, observe, and analyze nature, and this gave birth to the field of science. As far as the defined field of study now known as Epidemiology and Public Health, it can be argued that it began in 1854, with a cholera outbreak in the Soho district of London and a physician named John Snow (who knew more than nothing).


London’s cholera epidemic of the mid-1800’s reached the Soho district in late summer of ‘54. With both a high density of residents and a non-existent sanitary system, more than 600 residents died within two weeks—a mortality rate above 12 percent—and anyone who could leave fled Soho in terror before a mysterious, rapid, and particularly unpleasant death.

At the time of this particular cholera outbreak, the dominant theory for the spread of disease was still “miasma” or bad air emanating from rotting organic matter. While the germ theory of disease had slowly started growing traction in the scientific community, it was still far from widely accepted.

Dr. Snow was a proponent of this newer theory, as he had been suspicious of the water supply for several years. Despite the sentimental depictions of Victorian times people have today, in those days public sewer systems had barely matured from the medieval era and were extremely limited. Most homes in London had a cesspit beneath the house, and to keep it from exceeding capacity, residents collected bucketfuls and dumped it into the Thames.

John_SnowA true scientist, Snow took samples of the water and examined it using the means available to him. His dilemma was that he did not have the tools to identify what in the water was causing the epidemic. (While an Italian Physician named Philippo Pacini did in fact identify the pathogen responsible for cholera in 1854, his discovery was largely ignored in the heated debate between germ theory and miasma.) Snow turned to other methods to investigate his theory of water-borne transmission, and enlisted the help of the venerable Reverend Henry Whitehead, the Assistant Curate at St. Luke’s Parish in Soho, who knew the local community well and was trusted by the frightened residents.

Rev. Whitehead was quickly convinced by Dr. Snow’s theory of water-borne transmission, and the two conducted interviews throughout the district. In possession of the interview data, Dr. Snow then created his famous map of cholera cases, and various public pumps of the city where residents drew their drinking water. His map showed a startling correlation: Soho’s cholera cases coincided with the area around the Broad Street water pump.  There was also a correlation between cholera cases and water supplied by the Southwark and Vauxhall Waterworks Company, which drew water directly from the Thames and delivered it to certain homes in Soho.

Ever the rigorous scientist, Dr. Snow also investigated the anomalies in his data. For instance, 10 deaths occurred where another pump was closer; Whitehead and Snow were able to determine that of these 10, five cases were among individuals who preferred the water of the Broad Street pump although another was closer, and three cases were among children who attended a school near the pump. Another anomaly: not a single case of cholera had appeared among the monks in a local monastery. This anomaly was investigated and it was determined that the monks drank only beer, which ultimately served to reinforce Snow’s conclusions (and maybe made beer even more popular than before).      

Snow applied statistics to Whitehead’s information, in combination with his map, and the two presented their evidence to the local Soho civic authorities, who removed the pump’s handle the very next day to prevent further consumption of the dirty water. The cholera epidemic vanished.

No one today would question the relationship between contaminated water and disease – public sanitation systems have prevented more deaths than all other medical interventions combined. Unfortunately, at the time, the situation was more complicated. Snow could not link his data with biospecimens—Pacini’s microbe—and his research was criticized and dismissed by the prominent medical journal Lancet as well as countered by Dr. William Farr, who was an official in what we would call London’s “office of vital statistics.”

In keeping with miasma theory, Farr reasoned that soil at low elevations, especially near the banks of the River Thames, contained more organic matter which would explain why the concentration of deadly miasma would be greater nearer the Thames than in more distant, elevated, locations. He had already presented data and calculations in 1852 that supported miasma as the source of cholera. Based on Farr’s conclusions, London’s officials rejected Snow’s theory of water-borne micro-organisms and replaced the handle on the broad street pump.

We are still faced with a version of Dr. Snow’s dilemma: disease arises from a complex, overdetermined, spectrum of gene-gene and gene-environment and behavioral interactions. Our need for epidemiologic data from large, carefully constructed cohort studies is greater than ever, but demographic, outcome, and similar data are insufficient – we need the corresponding biological data from donor specimens.

Fisher BioServices is collaborating on and supporting some of the most significant cohort studies in operation today; we are actively and enthusiastically engaged in linking specimen data with cloud-based platforms, mobile devices, and other means of managing data efficiently, so that the biospecimens in our custody can be put to optimal use. This blog series is dedicated to the public health studies that give biological samples their ultimate worth.

Three more items worth noting:

  • It was later discovered that the Broad Street pump was within three feet of a contaminated cesspit that had begun leaking after the street was widened.
  • In 1883, when the germ theory of disease was almost universally accepted, German physician and bacteriologist Robert Koch “re-identified” the cholera microbe, to scientific acclaim. 
  • Broad Street has since become Broadwick Street, but Soho’s role in history has not been forgotten – a (dry) replica of the famous water pump was installed in the 1990s near the location of the original.  If you’re thirsty, try the John Snow pub around the corner. 

Public health research began with cholera, but it certainly didn't stop there. Stay tuned for our next episode in the Evolution of Public Health Series where we'll explore the microbiome. In the meantime, check out our eBook with Clive Green, Director and Head of Sample Management at AstraZeneca, regarding the challenges in the biospecimen supply chain, from both a small molecule and biospecimen perspective.

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