One of the past unsung heroes in medicine is John Snow, a pioneer in a number of fields.

Snow was a scientist, physician, pharmacologist and anesthesiologist, and likely the very first epidemiologist. His map of London during the cholera epidemic in 1854 epitomized research as it related to the transmission of disease.

He was born in York, England, in 1813, the son of a farmer. In private school it was reported that he was eager to learn and fond of mathematics. At the age of 14, he became a pupil of William Hardcastle, surgeon at Newcastle-on-Tyne, and studied at the Newcastle Infirmary.

As an apprentice in Newcastle, Snow saw the ravages of cholera firsthand when the disease struck in 1832. He treated the survivors of the outbreak in a local mine, and observed the unsanitary conditions there. The idea that the disease was rooted in the social conditions of these impoverished workers stayed with him throughout his career in medicine. Snow moved back to York in 1835 and then to London, where he enrolled in the Hunterian School of Medicine.

 In 1838, Snow received his apothecary (pharmacy) and surgeon’s licenses and established a successful general practice in London. Eventually Snow became an acute diagnostician and his colleagues regularly began consulting him about difficult cases. One area of interest in which Snow excelled was in the care and delivery of infants.



Anesthesia

Before the advent of anesthesia, John Snow was largely able to make a living as a general practitioner in London and still have time for research and medical society meetings. When the discovery of ether was announced to the world in 1846, his background and interest in respiration led him into a number of experimental systematic studies related to the mechanisms of action and the effects of ether and chloroform.  

Snow began experimenting with chloroform in 1847, and tried using it on himself. He found chloroform less pungent than ether, more economical, faster acting and more easily inhaled. His research was rewarding and soon Snow became the foremost anesthesiologist in London. One use that he espoused was in childbirth, whenever patients were anxious to be spared pain. This was the case when Snow was called to Buckingham Palace to administer chloroform to Queen Victoria, following her eighth pregnancy in March 1853. His attendance to the queen was momentous for Snow’s reputation. Prior to her delivery, the general attitude then was that women must bear children in the biblical manner, i.e., in sorrow.



Cholera

No one knows exactly what sequence of events turned John Snow’s interest toward cholera in the late 1840s. The disease, of course, was a constant presence in his life from at least the early 1830s when he was an apprentice in Newcastle. There may have been a direct link to his practice as an anesthesiologist, as chloroform had been wrongly championed as a potential cure for cholera.

The cholera outbreak of 1848, the most severe in more than a decade, made the disease one of the most urgent medical riddles of its time. Remarkably, in all of the discussions about cholera that had percolated through the popular and scientific press since the disease arrived on British soil in 1832, almost no one suggested that the disease might be transmitted by means of contaminated water. Snow appears to have been an interested listener rather than an active participant in the professional debates about the nature of cholera at least until an outbreak in 1854, when in a period of 10 days, more than 500 cases were reported.

The 1854 outbreak occurred despite a series of sanitary reforms that culminated in passage of the Public Health Act in 1848. So many casualties in so short of time suggested a central contaminated water source used by large numbers of people. The incidence of disease appeared to have occurred near the intersection of Cambridge and Broad streets, Golden Square. The number would have been considerably greater, no doubt, had not a large number of persons fled the city.

Snow embarked on what we now call an epidemiological study concentrating on the contamination of the water from the street pump on Broad Street. He personally visited the homes of 658 people who died of cholera, ascertaining the water supply to each house. Nearly all of the deaths had taken place within a short distance of the pump. His inquiry indicated that that there had been no particular outbreak or increase in cholera in this part of London, except among the persons who were in the habit of drinking the water from the Broad Street pump. He decided to graphically represent his findings with a map that circumscribed the center of the outbreak with black bars representing each death. This map continues to appear in textbooks and to grow in stature. Municipal authorities removed the pump handle the day after the report was issued.

Snow’s work on cholera illustrated a key epidemiology principle: that the most important information to have about any communicable disease is its mode of transmission.

Snow was voted the greatest doctor of all time in a March 2003 survey by Hospital Doctor magazine, with Hippocrates (460-370 B.C.) coming in second.

Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, will touch on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at maxsherman339@gmail.com.