Most people have heard that a wise doctor in London identified the source of the cholera contagion by plotting the location of the victims on a map. The clustering of the victims around particular wells revealed that cholera was spread through contaminated water. What people do not know is that despite the overwhelming evidence that was compiled it was only after decades that public authorities made use of this knowledge to end the epidemics. The reason for this delay is that a plausible but false theory of the source of the epidemics prevailed. That theory was that disease was caused by gaseous miasmas that were associated with foul smells and therefore if the foul smells were eliminated so would be the diseases. The doctor, whose name was John Snow, was a truth seeker and he relied upon empirical investigation. He found the truth. The advocates of the miasma theory were true believers who accepted the theory because of its plausibility and then sought evidence to support it even though they had to ignore evidence that contradicted it.

Cholera hit London in the fall of 1831. It had traveled for 15 years along the trade routes from India by way of China and Russia creating wide spread devastation along its way before hitting London. In that epidemic of 1831 six thousand died. The victims died suddenly and painfully. Its onset was severe diarrhea and vomiting leading to dehydration and ultimately kidney failure and death. One of the witnesses to the suffering was a young apprentice doctor named John Snow. This was a time before the germ theory of disease was established and people simply did not know what caused such illnesses. This did not mean that people didn't have beliefs about what caused disease. There was a plethora of beliefs strongly held such as that epidemics were divine punishment for general immorality. This religious notion was the why of epidemics and not contradictory to the various explanations of how the divine judgment was implemented.

One popular theory of ancient tradition was that diseases were caused by miasmas. This theory went back at least far as the ancient Greeks and was supported by the venerable intellects of church and state. It was clearly plausible. Bad smells were obvious evidence of something evil. Satan was identified by his sulfurous smell. For its believers the miasma theory needed no supporting evidence; it was obviously true. Evidence was only required to counter the competing theories.

John Snow was a rare person who really wanted to know the truth of the matter and was willing to keep an open mind until the truth was established by empirical evidence. Snow had come to London from Newcastle-upon-Tyne where he had served his apprenticeship as a physician. At that time there were no medical schools. One became a doctor by apprenticing oneself to a practicing doctor until one had learned the trade. Snow ultimately became a surgeon and he utilized the new notion of anesthesia in his practice. He had been practicing his trade from the Soho district in the central area of London for about ten years in 1848 when a new epidemic of cholera began. Ultimately thirty thousand Londoners contracted the disease.

London at that time had two to three million people. It was one of the largest and most important cities in the world. Despite being at the forefront of technology at the time London still had a primitive system for handling human wastes. Well not the most primitive, which would involve humans urinating and defecating wherever they saw fit. Next most primitive would involve humans defecating in chamber pots and the chamber pots being emptied wherever humans saw fit to do so. Next to that was the use of privies where a hole was dug in the ground and an outhouse built over it. When that hole was filled another was dug and the outhouse moved to it. Some of the feces and urine leached into the surrounding soil but because a minimal amount of fluid was involved it typically did not go very far. Then came the water closet, the flush toilet. This device was a great improvement in convenience but it had the disadvantage of creating a greater volume of liquid that had to be dealt with. The flush toilets emptied into cesspools which filled up with liquid far faster than the privy holes. Furthermore the flush water leached the contaminants to greater distances. The cesspools sometimes overfilled and overflowed. The cesspools had to be emptied periodically at substantial cost.

The system of flush toilets may have been the most up-to-date technology of the time but it had its problems. One problem was the smell that pervaded the city. This was the most prominent problem. The less prominent but more significant problem is that the leaching and overflows from the two hundred thousand cesspools of London contaminated the water supply from the wells. Hardly anyone was aware that this was a problem.

As the cost of emptying the cesspools rose with the growth of London there was more neglect of the cesspools.

A system of sewers had been built for London to handle the runoff of rain so as to prevent flooding. The storm drain system flowed into the Thames River. Some water companies supplying water to various sections of London drew water from the Thames. Until 1815 the overflows from the cesspools was not permitted to flow into this storm drain system. By the 1840's there was a concern for creating a sewer system that would take human wastes and the noxious smells away from London and dump them into the Thames where they would hopefully be carried out to sea. The term hopefully was appropriate because the Thames is tidal and when the tide was flowing in the wastes would be carried upstream rather than out into the English Channel.

The people who desperately wanted to get rid of the terrible smells found the miasma theory of disease useful for providing a clenching argument for getting rid of the cesspools. It is similar to the people who objected to the smell of smoking in public places glomming onto the theory of second-hand smoke causing cancer.

The miasmic theory of disease and need for sewers to remove human wastes from the city had notably prominent advocates. Florence Nightingale was one. A lawyer active in public affairs, named Edwin Chadwick, was another. Chadwick claimed that the incidence of disease among the poor was due to inadequate ventilation for removing the smells in their dwellings. According to Chadwick, "All smell is disease." Another important public figure who was an advocate of the miasma theory of disease was William Farr, who was the chief statistician of the Office of Registrar General, the office that recorded deaths in London.

John Snow quietly compiled his own statistical information. In addition to plotting the incidence of cholera deaths on a map, he went around surveying people. Once he came to the conclusion that cholera was spread from particular wells he had to deal with the cases of deaths to people not living close to those wells. By interviewing the families of such victims he found that in deed those people had drunk water from the suspect wells. Snow also interviewed the people who worked in the sewer tunnels. These were the people who, if the miasma theory of disease were correct, would be the first victims of disease. Instead during the cholera epidemic these sewer workers were untouched by cholera. They happened to be from areas where their water source was uncontaminated.

Cholera struck the middle class and rich as well as the poor. In the case of the middle and upper classes they often got their water piped into their homes by water companies. These water companies however typically drew their water from the Thames River, the same river that was receiving sewage outflows from the city. The water companies filtered the water and took clarity to be evidence of purity. It is no wonder that the middle and upper classes were struck down by cholera; they were drinking diluted sewage.

But the poor were more heavily devastated by the cholera epidemic. They lived eight to ten to a room and they did not have the funds to bury their dead right away so when a member died the body had to be kept in the same room until they found the means to arrange the burial.

By the end of the 1848-49 cholera epidemic fourteen thousand had died in London. By that time John Snow felt he had overwhelming evidence that cholera was spread through water from sewer contamination. He wrote a paper entitled On the Mode of Communication of Cholera, which should have been the initiation of a campaign to wipe out cholera. Instead his message fell on deaf ears. John Snow was a quiet, shy person. His personality was no match for the loud-mouthed lawyer types like Edwin Chadwick who were preaching the miasmic theory of disease.

In 1853 there was another cholera epidemic. John Snow continued his investigations and found one well on Broad Street near his Soho office that was apparently responsible for hundreds of cholera attacks in a ten day period. He took his evidence to the local parish authorities and the pump handle was removed from that well. But that was one of the few cases in which authorities took his evidence seriously. Instead Edwin Chadwick and William Farr, the head of the Office of Registrar General, publically denounced Snow's theory of the source of cholera.

The advocates of the miasma theory were campaigning for a comprehensive sewer system for London. But due to lack of funding from Parliament this was not being achieved. However in the hot, dry summer of 1858 the smell became overwhelming. It was called The Great Stink. The members of Parliament believing that they were at risk of contracting lethal diseases from the smell passed legislation funding the completion of the sewer system. The smell from the river came from the outflow of existing sewers into the Thames within the city. The sewage system needed an extension downstream beyond the city. The completion of the sewer system was an essential part of eliminating the contamination of the water system but only if water was not drawn from the river where it was contaminated by the city's sewage. This was nine years after Snow had published his paper on the source of the cholera contagion. Unfortunately his great work had convinced no one of authority or significance. During the Great Stink John Snow suffered a stroke and died at age 45.

The comprehensive sewer system with its extension to take the outflow downstream beyond the city was completed in 1866. It had gotten rid of the miasma. But to the consternation of the true believers in the miasma theory after the completion there were new cholera deaths. William Farr, the official statistician who had publically denounced Snow's theory of the water-borne transmission of cholera looked at the statistics and found that the outbreak was in an area supplied by a water company that drew its water from the river where it was contaminated by sewage. Despite the filtering and the clarity of the water it was contaminated by some agent that produced cholera. William Farr recognized that cholera was water-borne and became a vociferous advocate for the theory which Snow had proven 18 long years before. Working from the correct theory the authorities were able to quickly take the necessary steps to contain the new cholera outbreak.