September 19, 2020

Snow and Whitehead, cholera detectives in 19th century London

Paradoxically, one of the reasons for the deterioration of public health in 19th century London was the widespread use of the toilet. A good part of its population no longer had to look for a less crowded place between houses to evacuate their intestines or to do it in a bucket whose contents were then thrown out the window. There was no doubt that there was an inexhaustible demand for the contraption. 827,000 people used the portable toilets installed in Hyde Park during the World’s Fair of 1851.

However, there was no sewer network that could absorb that river of waste. All ended up deposited in the cesspools that already existed and that were emptied periodically. The risk that they would end up contaminating the drinking water supply was very real, as could be seen in the middle of the century with the cholera epidemic of 1856. Of course, at that time no one thought that an infectious disease could spread through water.

London was then a great mountain of shit, in direct terms. It was the result of great demographic growth –2.4 million inhabitants in the 1851 census, the largest city on the planet– and the appalling living conditions of its poorest population. There wasn’t even room for the dead. In Islington, a northern neighborhood, a cemetery with capacity for about 3,000 corpses housed 80,000. London “was drowning in its own filth,” writes Steven Johnson in the book ‘The ghost map’, published in Spain by Captain Swing.

Throughout its history, London had known several epidemics in the face of which the only sure solution to survive was to flee the city. This is what Henry VIII did every time the plague returned to the capital of his kingdom, and he did it frequently. The 19th century was a time of constant scientific and technological advances, but science was still moving along winding roads. The cholera epidemic of 1854 was an essential moment not because of the number of deaths – it had suffered many worse – but because it finally forced a change in the established vision of the origin of the disease. This great scientific leap was made possible by two men, the anesthesiologist John Snow and the Reverend Henry Whitehead, the main protagonists of the book.

Steven Johnson explains that Victorian medicine was not very supportive of the scientific method. It had been taken as a dogma that a disease like cholera was transmitted through the air, a kind of failed antecedent of the form of contagion of other pathogens unknown at the time. The so-called miasmas happened to be the lethal effluvia that arose from the concentration of human and animal residues, perfectly distinguishable by smell, which thus became the main diagnostic tool. The terrible living and hygienic conditions of the most disadvantaged Londoners seemed to confirm this hypothesis. “Purifying the air in the sick room” was one of the remedies that was publicized in the press of the time, which had a rich source of income in the advertising of miracle pseudo-drugs. Science with capital letters was not very demanding either. “The most repeated phrase among Victorian doctors was simply: ‘Take a couple of doses of opium and call me in the morning.’

This is what happened when the 1854 epidemic broke out. Johnson places us at the home of Thomas and Sarah Lewis when their second daughter, a six-month-old baby, begins to fall ill. Not many details of the case are known, but enough to find an explanation for the origin of the outbreak: “While waiting (for the doctor), the woman soaked the dirty diapers in a bucket of warm water. Sarah Lewis took advantage of the few moments in that the girl fell asleep to go down to the basement of the house and throw the dirty water into the cesspool located in the front part “.

Dr. John Snow was a physician with a passion for research. His role was crucial in finding the best way to manage ether and then chloroform in operations. As an anesthesiologist, he became almost a celebrity. Queen Victoria requested his presence at the delivery of her eighth child. She had reached the peak of her professional career, but decided to go further. She went on to deal with an activity that did not yet exist at that time: epidemiology.

He observed the cholera epidemic of 1848 – 50,000 deaths in two years – and came to the conclusion that the pathogen could not be in the air and that it was not transmitted by simple proximity. “It was ingested by the victims, either through direct contact with the fecal waters of other patients or, more likely, through water contaminated with these wastes.” John Snow’s research work in the field allowed him to discover that two nearby houses with families with occupants of similar social conditions suffered a very different incidence of the disease. The reason was that they “got their water from different sources.”

The reaction in the scientific community to Snow’s new ideas “was positive, but skeptical,” Johnson writes. He needed more evidence. To obtain them, he had to wait for the outbreak of 1854, which originated ten blocks from his office. The doctor repeated his investigative work, entered Soho – a place that upper-class Londoners dared not enter – and began to look at the Broad Street water feature. This crystal-clear and high-quality water was consumed by many residents of that area.

Snow began to accumulate revealing facts. A home for the poor in the area where no one had gotten sick, because he had a private water supply that came from a company that Snow knew was reliable. A brewery that had its own private well and in which the workers did not drink much water on their shifts as they had plenty of beer on the premises. Two women who lived far from the area and who died of cholera, because they received the water they consumed from a relative who collected it from the Broad Street fountain.

At the same time that Snow added new evidence, so was the Reverend Henry Whitehead, a priest used to kicking Soho to see how his parishioners lived. In that sense, he was an accidental researcher, without scientific training but with a keen sense of observation and ability to listen to patients. Initially, he did not share Snow’s views, although he soon saw that they matched what he was observing on the streets. The work of the priest, including a monograph he wrote, was important for the Parish Board of the area to decide to form a committee for the investigation of the Broad Street outbreak that carried out field work in the neighborhood with a questionnaire that they should fill out the neighbors.

Just like now, they put the trackers to work. It was then that Whitehead realized that the elderly widows who had survived the epidemic owed their lives to “having no one to fetch them water” from the Broad Street fountain. New data led to an investigation into the state of the cesspool used by the Lewis family who had lost their daughter Sarah three days before the outbreak began. There they discovered that the poor quality of its construction had prevented it from evacuating its contents into a sewer and had brought it into contact with the well on Broad Street from which the spring water came out.

Snow still had time to star in another innovation. With his data and that of other sources, he created a map, of which he made several versions, to include the location of the water sources and the number of houses where cases of cholera had occurred. “The visual impact of that map was astonishing,” says Johnson, showing that the cholera “had been radiated from a single point.” Snow was also a pioneer of infographics and the visual explanation of data.

All his discoveries and those of Whitehead could have been an immediate success, but going against the mainstream does not usually grant such satisfactions. “Do you have facts to prove the validity of your theory? No!” Replied an editorial in The Lancet. The miasmatic current was firmly established in the political and scientific elites, and they were not going to give way easily.

Had to occur The Great Stench of 1858 – weeks of awful smell coming from the Thames and forcing Parliament to close – for the miasma theory to be widely questioned. All that pestilence did not cause any increase in mortality. Snow could not claim victory. He died on the same dates of a stroke at the age of 45. Investigation of a later and more serious cholera epidemic in 1866 ended up confirming the conclusions of Snow’s work.

Science sometimes holds obvious triumphs. A few weeks ago, the WHO declared Africa free of polio. However, social and economic conditions play a basic role, and there science is not enough. “It is possible that neither of us will live to witness the day and my name will no longer be remembered by the time it arrives,” Snow told Whitehead in conversation, “but the day will come when major outbreaks of cholera will be the business of the world. past, and it is the knowledge of the way in which the disease spreads that will determine its disappearance. ”

Steven Johnson recalls in the book that today more than a billion people do not have access to safe drinking water around the planet, which is the source of many diseases, including cholera. John Snow’s dream still has a long time to come to pass.


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