Stream 1 - Introduction
a: Encyclopedia Entry and "Greatest Doctor"
Encyclopedia Entry for John Snow
A summary of John Snow's life in Encyclopedia Britannica is a good starting point for exploring the extensive
material on the life and times of John Snow that are here presented. Yet before getting underway, two points regarding the author should be kept in mind, illustrated with an investigation triangle and a triad- plus- one figure, both well known to epidemiologists.
Like other epidemiologists, when conducting a field investigation, author Frerichs starts by considering who was impacted ("person"), the location or locations of occurrence ("place") and when it occurred ("time"). In this instance, your storyteller focused on John Snow as the "person," as well as members of his extended family, various friends and many professional colleagues. Maps and images are widely used throughout to give you a sense of "place," and the months and years of events moor everything in "time."
When studying the dynamics of infectious disease transmission, epidemiologist are taught to keep a triad in mind, namely a diagram of the interplay or communication between the disease agent, the human or animal host, and the environment in which the agent and host reside. Since vectors for some infectious diseases come into play, the triad plus one (upper left) is usually deemed more appropriate for certain diseases. If cholera is being studied in current times (upper middle),the bacterial agent Vibrio cholerae is known, with serogroups O1 or O139 being the most common sources of epidemics or pandemics. These two are toxigenic forms that do major damage, liberating a toxin that harms cells in the gastrointestinal tract. As biological or mechanical vectors of transmission, copepods, shellfish or houseflies can also play a role in spreading the bacteria.
John Snow may have had a triad in mind when he studied cholera in the mid-1800s (upper right), but he had no definitive knowledge of the agent (perhaps a cell-like organism, he thought), and certainly no possible vectors. All that was clear was the host and the environment and the communication or interplay between the two, but that was enough for him to leave his indelible mark, once history caught up to the truthfulness of his insights and achievements. As you will learn, Snow's seminal epidemiological book (1855) was entitled, On the Mode of Communication of Cholera, not simply, On Cholera. That is, his epidemiological focus was on the interplay or communication between host and environment that resulted in cholera. He had his hypotheses, but needed more, as exemplified by his extensive and steadfast field work
Source: Encyclopedia Britannica, August, 2025.
John Snow - British physician and Epidemiologist
by Ralph R. Frerichs, Professor Emeritus in the Department of Epidemiology at University of California, Los Angeles (UCLA).
John Snow (born March 15, 1813, York, Yorkshire, England—died June 16, 1858, London) was an English physician known for his seminal studies of cholera and widely viewed as the father of contemporary epidemiology. His best-known studies include his investigation of London’s Broad Street pump outbreak, which occurred in 1854, and his “Grand Experiment,” a study comparing waterborne cholera cases in two regions of the city—one receiving sewage-contaminated water and the other receiving relatively clean water. Snow’s innovative reasoning and approach to the control of this deadly disease remain valid and are considered exemplary for epidemiologists throughout the world. Snow’s reputation in anesthesiology, specifically in regard to his knowledge of ether and chloroform, was considerable, such that he was asked to administer chloroform to Queen Victoria when she gave birth in 1853 to Prince Leopold and in 1857 to Princess Beatrice. Snow’s achievements are considered remarkable, given his humble origin and short life.
Education and contributions to anesthesiology
Snow was born in York, England, where his father worked as a labourer in a coal yard. He was the firstborn in a family of nine children. At age 14, after spending his early years at a school in York, he left home and pursued three consecutive medical apprenticeships in various regions of Yorkshire. In 1831, when visiting coal miners, he had his first encounter with cholera, a disease that would later become the focus of his scientific endeavours. By 1836 Snow had begun his formal medical education, eventually receiving a doctor of medicine degree (1844) from the University of London. In 1850 he became a licentiate (licensed specialist) of the Royal College of Physicians of London, rising to a higher level in the medical profession. He lived, conducted research, and maintained a medical practice in the Soho neighbourhood of London.
In 1846 Snow learned of the use of ether in America to relieve pain during surgery. He soon mastered its use, and in 1847 he was appointed as anesthesiologist at St. George’s Hospital. Later that year he started working with chloroform. Finding the prevailing drops-in-handkerchief method to be too crude, he developed an apparatus that improved both the safety and the effectiveness of chloroform. His success with administering chloroform to Queen Victoria produced a dramatic increase in the social acceptance of gaseous anesthesia. Snow spoke extensively on his work with anesthetics and wrote the influential book On Chloroform and Other Anaesthetics, which was published shortly after his death in 1858.
Broad Street pump and the “Grand Experiment”
Many British physicians investigated the epidemiology of cholera. The first cholera epidemic in London occurred in 1831–32, when Snow was still learning his craft. When the second cholera epidemic occurred, in 1848–49, he and others founded the London Epidemiological Society, intending to advise the government on ways to combat the disease. Snow reasoned that cholera was caused by a microbelike agent, or germ, that was spread through direct fecal contact, contaminated water, and soiled clothing. However, his theory was at odds with the then prevailing theory that cholera was spread by bad air, or miasma, arising from decayed organic matter. The two etiologic hypotheses—germ theory and miasma—were widely debated, with available clinical and population-based evidence serving as the basis for arguments from both sides. The etiologic debate raged for many years. It was not until the causative organism, Vibrio cholerae (initially discovered in 1854), was well characterized in the 1880s that the debate was decided in favour of the germ theory.
Snow’s respected reputation in epidemiology arose from two classic studies of the third epidemic to reach England, which began in 1853 and lasted until 1855. The first study concerned the Broad Street pump outbreak of 1854, which killed many persons in the Soho neighbourhood. He used skilled reasoning, graphs, and maps to demonstrate the impact of the contaminated water coming from the Broad Street pump. The second study was the “Grand Experiment,” also of 1854, which compared London neighbourhoods receiving water from two different companies. One company relied on inlets coming from the upper River Thames, located away from urban pollution, and the other company relied on inlets in the heart of London, where the contamination of water with sewage was common. Snow showed the harmful effect of contaminated water in two nearly equivalent populations, and he suggested intervention strategies to control the epidemic. His ideas and observations, including innovative disease maps, were published in his book On the Mode of Communication of Cholera (1855). Later, in the 1930s, Snow’s work was republished as a classic work in epidemiology, resulting in lasting recognition of his work.
Additional Reading
A work focusing on Snow’s study of the Broad Street pump in the Soho neighbourhood of London is Sandra Hempel, The Strange Case of the Broad Street Pump: John Snow and the Mystery of Cholera (2007).
An extensive, detailed account of Snow’s life is Peter Vinten-Johansen et al., Cholera, Chloroform, and the Science of Medicine: A Life of John Snow (2003).
A narrative of the cholera epidemics of 19th-century London that covers the significance of Snow’s outbreak maps is Steven Johnson, The Ghost Map: The Story of London’s Most Terrifying Epidemic—and How It Changed Science, Cities, and the Modern World (2007).
John Snow as "Greatest Doctor"
In a March 2003 survey by Hospital Doctor magazine, a United Kingdom -based publication for hospital doctors, John Snow was voted the "greatest doctor" of all time, with Hippocrates (460-370 BC) coming in second. While the poll was likely biased with over-representation of John Snow supporters, the findings do point to the increased prominence of Dr. Snow among contemporary physicians.
Source: Worlds Greatest Doctor, Hospital Doctor 64(3), March, 2003. Cited in: Editorial, General or specific? International Journal of Epidemiology 32(3), June 2003, p. 331.
Dr John Snow Named the Greatest Doctor
Dr John Snow has been voted the greatest doctor ever in a Hospital Doctor poll.
Readers were invited to consider a number of doctors worthy of the title, but it was the nomination of Dr Snow by Dr Guy Jackson, a research fellow in anaesthesia in London, that attracted the most support. He was backed by an active campaign from the John Snow Society.
Dr Snow (1813-1858), a GP based in Soho, developed the technique of anaesthesia. According to Dr Jackson, Dr Snow's book On The Inhalation Of The Ether Vapours "was the definitive work of its day, using scientific principles and practice more akin to those used today than those used by his contemporaries." He was called on by Queen Victoria to provide analgesia for childbirth. She described his care as "most efficacious." Dr Snow also developed drugs including chloroform, theories on the transmission of cholera, and was seen as one of the founders of intensive care medicine.
In second place was Hippocrates (460-370BC), who taught that illness was not down to the influence of evil spirits and that doctors could help through evidence-based medicine. He wrote more than 70 books and introduced the oath.
Dame Cicely Saunders (1918-2005), founder of the modern hospice movement, came third.
Click to continue to Stream 1 - b: Images and Medal of Snow
