When the industrial revolution took hold of England, the countryside emptied. Laborers flooded cities seeking work. In 1700, Manchester’s population was less than 10,000.¹ By 1801, Greater Manchester was home to more than 330,000 people. And by 1851, its population had surpassed one million. London experienced similar growth. Already home to more than one million people in 1801, London reached 2.6 million just fifty years later.² The census of 1851 marked a turning point: for the first time in its history, England had become a predominantly urban nation. By the time of Queen Victoria’s death in 1901, eighty percent of England’s population lived in urban areas.³

As the workers arrived, English cities faced a new problem: a housing shortage. The newly arrived workers accepted whatever meager lodging they could find. As long as it was near enough to the factories, mills, or docks, any place to sleep would suffice.

You can imagine the conditions. Tiny cramped tenements. Often no sanitation other than a backyard, a side alley, or a streetside cesspool. Sometimes no windows and very little natural light. Consider the following excerpt from Dr. Baron Howard’s 1842 account of lodging houses in Manchester.⁴ Howard wrote:

Not only did the arrival of workers outpace housing, it often outpaced jobs. Some went weeks, or longer, without finding work. And most who did find work were merely scraping by. We often associate the hardships of the Industrial Revolution with factory workers and day laborers. To be sure, these were dirty and dangerous jobs. There were many jobs, however, that were dirtier, more dangerous, and even less well-paid. For instance, pure finders searched city streets for dog feces (used in the leather tanning process) and mudlarks (often children) searched the banks of the Thames at low tide for anything that could be collected and sold. For the laboring classes, injury, illness, and poverty became as common as the filth and stench of the city.

In an attempt to cure the social ills of the day, social reformers stepped in with a host of new policies. Few of these reformers were more influential than Edwin Chadwick. Born in industrial Manchester, Chadwick was no stranger to the filth of Victorian-era cities. At age 18, he moved to London to study law and became a barrister. In London he came to know the intellectual elite of the day, including economist John Stuart Mill, health and social reformer Dr. Thomas Southwood Smith, and utilitarian philosopher Jeremy Bentham.⁵

In 1832, Prime Minister Earl Grey created the Royal Commission of Enquiry on Poor Law. Chadwick was appointed assistant commissioner, and he played a leading role writing England’s new Poor Laws.⁶ As a Bentham acolyte, he believed strongly in free choice and individual responsibility. He helped shape the New Poor Law around the workhouse system. Able-bodied people seeking public assistance were generally required to enter a workhouse (fig. 6), where food and shelter were provided in exchange for labor. The workhouses themselves were designed to be so squalid, the work so arduous, and the food so wretched, that they would appeal only to the most destitute. Those who declined to enter received no relief. As explained in the Poor Law Commissioners’ Report of 1834, “If the claimant does not comply with the terms on which relief is given to the destitute, he gets nothing; and if he does comply, the compliance proves the truth of the claim — namely, his destitution.”⁷

The brutality of these laws was evident to many critics at the time (fig. 7). Charles Dickens captures their cruelty in the second chapter of Oliver Twist, first serialized in February 1837: “So, they established the rule, that all poor people should have the alternative (for they would compel nobody, not they,) of being starved by a gradual process in the house, or by a quick one out of it.”⁸

From Poor Laws to Public Health

After the Poor Laws went into effect, Chadwick turned his attention to another primary concern of the period: illness and disease. Since the time of Hippocrates, many believed that disease arose from the noxious smells of decaying carcasses, rotting food, and human waste. This belief, known as miasma theory, dominated medical thinking for more than two thousand years. In nineteenth-century England, prominent reformers embraced miasma theory. Florence Nightingale attributed a host of diseases to the practice of placing drains beneath homes, from which odors could escape and infect inhabitants.⁹ Chadwick himself testified before Parliament, “All smell is, if it be intense, immediate acute disease…”¹⁰

People went to remarkable lengths to eliminate noxious odors and purify the air around them (fig. 9). During England’s first cholera outbreak in 1832, surgeon Thomas Calley wrote to the Central Board of Health, “I am persuaded that nothing would destroy malaria equal to the combustion of gunpowder from large pieces of ordnance on the principal [sic] that it would produce a general rarefaction of the atmosphere and fill the element with vital air.”¹¹ Those who could afford them carried nosegays, small bouquets of aromatic flowers or strongly scented herbs, often held in small vases called tussie-mussies. The pleasant smell was believed to ward off disease.¹²

Miasma theory was not entirely without empirical basis. People living in polluted, foul-smelling areas got sick more frequently than those who lived in cleaner, wealthier neighborhoods. This was particularly true in low-lying areas, where human and animal waste collected in stagnant water. As William Farr documented in his Report on the Mortality of Cholera 1848–49, there were fewer cholera deaths at higher elevations.¹³

Miasma theory, however, mistook correlation for causation. Although unknown at the time, the cholera outbreaks documented by Farr were caused by traces of human fecal matter passing from person to person through water contaminated with a particular bacterium. When factory workers and day laborers lived together in crowded tenements or lodging houses without adequate sanitation, disease spread quickly.

Chadwick had his theory wrong, but he had a viable plan to prevent disease: clean up English cities. First, though, he needed to demonstrate a link between poor sanitation and disease.

In 1842, Chadwick published his Report on the Sanitary Condition of the Labouring Population of Great Britain, which documented startling rates of infectious disease mortality across populations. In 1838, for example, England and Wales recorded a total of 342,529 deaths. Of these deaths, 35,564 were attributed to old age, 12,055 to violence, and 282,940 to disease.¹⁴ In a single year, disease claimed nearly two percent of the population of England and Wales. And this rate was typical for the period. As Chadwick had suspected, infectious disease mortality was more common in impoverished neighborhoods.

Although Dickens criticized the Poor Laws, he and Chadwick became unexpected allies in promoting sanitation as a means of preventing illness. After reading Chadwick’s sanitary report, Dickens wrote to a mutual friend, “Pray tell Mr. Chadwick that... I heartily concur with him in the great importance and interest of the subject though I do differ with him, to the death, on his crack topic — the new Poor Law.”¹⁵

Shortly after meeting Chadwick in person, Dickens began including issues of miasma and cleanliness in his fiction, including his novel Dombey and Son. He also founded the periodical Household Words, which promoted the goals of the sanitary movement.¹⁶

Chadwick believed the solution was simple: encourage habits of cleanliness, improve ventilation in housing, and most important, provide clean water. Otherwise, England would continue the status quo where “the annual loss of life from filth and bad ventilation are greater than the loss from death or wounds in any wars in which the country has been engaged in modern times.”¹⁷

Chadwick set out to clean up London’s downtrodden neighborhoods. His efforts laid the foundation for one of the greatest public works projects of history: Sir Joseph Bazalgette’s creation of the London sewer system, constructed after the “Great Stink” of 1858. Between Chadwick and Bazalgette, however, London suffered another great cholera epidemic. Its investigation would fundamentally reshape scientific understanding of cholera in particular and disease transmission in general.

From Miasma Theory to Germ Theory

Although the majority of the population believed in miasma theory, there was a small contingent of skeptics. Notable among them was John Snow, a prominent physician. Snow was born in York where his father labored in a coal yard. The neighborhood of Snow’s youth was exactly the sort of place where people like Chadwick expected disease to flourish.

After nearly a decade as an apprentice to a surgeon and apothecary, Snow walked more than 400 miles to London to attend medical school. Upon completion of his training, Snow practiced as a general physician in London’s Soho neighborhood, where he also lived. He soon became known for his pioneering use of ether and chloroform as general anesthetics. Snow’s expertise became so well established that he was enlisted to anesthetize Queen Victoria during the births of two of her children: Leopold in 1853 and Beatrice in 1857.¹⁸

Despite these accomplishments, Snow is best remembered for his investigation of the 1854 Soho cholera outbreak, which killed more than 500 Londoners in just ten days. Of the ordeal, Snow wrote, “The most terrible outbreak of cholera which ever occurred in this kingdom, is probably that which took place in Broad Street, Golden Square, and the adjoining streets, a few weeks ago.”¹⁹

Snow rejected miasma theory, believing instead that cholera was transmitted through contaminated water. Famously, during the 1854 outbreak, Snow recorded each cholera victim with a dash on a map (fig. 12). He found that most cholera victims lived closest to the water pump at the intersection of Cambridge and Broad Streets. But there were exceptions. Some had a closer source of water, while others living near the Broad Street pump never contracted the disease.

Snow set out to understand these exceptions. Going door-to-door, he asked residents where they obtained their water. One by one, the answers confirmed his hypothesis. Several homes used the Broad Street pump despite a nearer pump because they preferred the taste of its water. A nearby brewery had only a few minor cases. Snow learned that the men working at the brewery were given liquor to drink. According to the proprietor, Mr. Huggins, the men “do not drink water at all.”²⁰ Even cases far from Soho were connected to Broad Street. One elderly cholera victim in the West End had her water delivered from Broad Street daily because she liked the taste. Her niece, from the “high and healthy part of Islington,” died after visiting her aunt and also drinking the Broad Street water.²¹ Snow painstakingly traced each case back to the Broad Street pump.

With the evidence in hand, Snow approached the local Board of Governors of St. James Parish on 7 September 1854. The board agreed to remove the pump handle the next day.²² The outbreak soon subsided. Snow’s investigation provided powerful evidence that cholera was transmitted through contaminated water. Most remained unconvinced — including much of the medical community.

In particular, local Reverend Henry Whitehead wrote his own account of the epidemic. A firm believer in miasma theory, he began interviewing witnesses to prove Snow wrong. Inadvertently, he discovered that a cesspool at the home of one of the earliest victims — a baby girl named Frances Lewis — sat only three feet away from the Broad Street pump.²³ At Whitehead’s urging, the Medical Committee of the Board of Guardians excavated the street in front of the Lewis home. They found decayed brickwork in the cesspool, which allowed waste to leak into the well of the Broad Street pump. Whitehead set out to prove Snow wrong but ended up proving him right.

Nevertheless, leading medical theorists remained committed to miasma theory. Snow was respected enough to treat Queen Victoria, but he lacked the standing of the era’s leading medical authorities. And Whitehead, although influential within Soho, was a local priest. Also overlooked by the establishment in Europe was an Italian scientist, Filippo Pacini. In 1854, the same year as the Soho outbreak, Pacini identified the consistent presence of a particular bacterium in the intestines of deceased cholera victims. He named this bacterium Vibrio cholerae.²⁴

As the years marched forward, cholera faded into London history: not because of a single discovery, but through the slow convergence of sanitary reform, public works, and broader improvements in water quality and hygiene. Chadwick and other reformers reshaped public attitudes toward sanitation. Bazalgette’s sewer system reshaped the city itself. Together, these efforts gradually brought London’s cholera epidemics to an end.

Today Snow is celebrated as a pioneer in the fields of epidemiology and public health. Popular history, however, has a habit of compressing decades of incremental progress into a single defining moment. We imagine one breakthrough overturning centuries of accepted wisdom, and our understanding of the world changes in an instant. The history of cholera tells a different story. Miasma theory faded over time, but its decline was measured in decades, not days.

Neither Snow nor Pacini lived to see their work fully embraced. Snow died of a stroke in 1858. Pacini died twenty-five years later, in 1883, still largely unknown outside Italy. The following year, German scientist Robert Koch conclusively demonstrated that Vibrio cholerae was the cause of cholera. Laboratory evidence had finally caught up with the conclusions that Snow, Whitehead, and Pacini had reached decades earlier.²⁵