It is late August 1854 in the city of London. An infant girl becomes ill and dies a day later. Within a week, dozens more deaths are being recorded within the parish. Cholera has broken out. While cholera has been known in other parts of the world, the first epidemic to hit England came in 1831. Another serious epidemic hit just six years earlier, in 1848-1849. What action should be taken to combat the disease and halt the crisis? That all depends on your understanding of what cholera is and how it spreads.
The Ghost Map: The Story of London's Most Terrifying Epidemic and How it Changed Science, Cities, and the Modern World, written by Steven Johnson, is a history of the responses to the 1854 cholera epidemic. Written almost in the form of a mystery novel, it is a fascinating look into the interrelationship of science, public policy, consensus thinking, cultural values and prejudices, epidemiology, demographic statistics, and sociology (and I'm sure there are some other –ologies I've missed.)
The consensus view of both scientists and the public in 1854 was Miasma Theory: cholera is spread by odors and vapors. In recent decades, England had experienced considerable urbanization. The poor lived in sections of cities that make "unsanitary" seem like a gracious term. Wastewater was not separate from drinking water. Contamination of well water was the norm. The stench of the city, especially in the poor areas, was potent. Diseases and epidemics were much more prevalent in the environs of the poor. A correlation was made between the stench from these neighborhoods and disease prevalence. The poor were frequently blamed for their living conditions and, thus, the diseases.
Johnson quotes from Florence Nightingale's 1857, Notes on Nursing manual, where she emphasizes pure air as the single most important focus for a nurse in caring for patients. Ventilating rooms and evacuating sewers of vaporous matter were top priorities. Her experience during the Crimean War showed that such actions drastically reduced death from diseases, including cholera. The evidence was overwhelming that cholera was an airborne disease. Yet the interpretation of the evidence was completely wrong. Enter John Snow.
John Snow was an overachieving working-class boy who became one of England's most noted physicians and scientists. He was a pioneer in developing anesthesia. He was called upon by Queen Victoria to personally apply his techniques in the birth of her eighth child in 1853. From study of the 1848-1849 cholera epidemic and other studies, Snow had developed skepticism about the Miasma Theory. Not the least of his questions was why people who made their livings scavenging through the sewage amid all the vapors seemed no more affected by these vapors than others in the community. He immediately set to work when he became aware of the 1854 outbreak, starting blocks from his home.
Snow tirelessly tracked down the sequence of deaths, plotted their locations, interviewed survivors of the dead, and gathered details of each incidence, looking for commonalities and incongruities. He made extensive use of death registries. He would later map these out and create the famous Ghost Map, the graphic that illustrated the spatial relationship of the deaths. But his immediate conclusion was that the cholera epidemic was somehow connected with the Broad Street water well. He recommended to the local governing board that the pump handle be removed from the pump to stop use of the well. The board was incredulous of his conclusions but figured it couldn't hurt. In addition to their own actions, they removed the handle over the protest of many residents, and the epidemic subsided.
Snow continued to analyze the data and disseminate his findings in the weeks and months following the epidemic. Meanwhile, Henry Whitehead, the minister for the parish in which the epidemic had hit and a solid believer in the Miasma Theory, had kept a diary of his visits to the ill and dying in the parish. He began to scrutinize Snow's work and raised objections. Eventually, the back and forth between Whitehead and Snow convinced Whitehead of Snow's position. He even gave testimony along with Snow to Parliament in 1855. Government officials were dismissive.
In the years immediately following the epidemic, Snow is absent from the official record of what happened. The epidemic was still viewed as a result of vapors. Snow died in June 1858, and no comment is made in his obituary of his connection with the cholera epidemic. But ironically, it was in the summer of 1858 that London experienced the "Great Stink," apparently a heat inversion that trapped all the odors of the city to the ground for an extended period. According to the Miasma theory, there should have been a dramatic uptick in the various diseases associated with odors. But William Farr, the city demographer and strong critic of Snow, detected no changes.
The Great Stink did set in motion another important set of events. It finally got the government to allocate the money to clean up the Thames and install a water and sewage system that would bring fresh water into the city and take the wastewater out, thus improving the drinking water quality and removing the stench. The project was completed in 1865, but another episode of cholera broke out just as it was being completed. Miasma theorists immediately seized upon this as evidence that vapors were causing the illness because the new water system would have prevented contamination.
Rev. Whitehead was called in to join a team to investigate the outbreak. They quickly isolated the outbreak's origin using Snow's analysis and began to inquire about the water sources. It turned out that the water system had been put in place, but one last pumping station was still under construction as the epidemic broke out. The epidemic emerged from precisely this location. William Farr became a radical convert to the point that some believe he rewrote the history of Snow's impact on the situation between 1854 and 1866. It would not be until years later that the microscopic cause of the disease would begin to be detected.
In some ways, this story is not dissimilar to countless others I've read about scientific discovery and adaptation. What is unique is Johnson's exceptional storytelling skills. It is a wonderful example of how change occurs in society as it interacts with science. For this reason, and for its ability to transport us back to another era, the book is worth the read. But it also has valuable lessons for science and public policy today.
Open and vigorous debate about scientific questions is essential to making sound policy decisions. In 1854, the consensus about cholera that had emerged in England over the previous two decades was that vapors transmitted it. Snow, a top scientist, and physician of his time, was ridiculed as a fringe crackpot by most other scientists and politicians. The correlation between vapors and cholera was an indisputable link. Furthermore, the production of these vapors and orders dovetailed nicely with society's prejudices about the irresponsible poor and their living habits.
But imagine what would have happened if Snow had not challenged the consensus or if others had not furthered his challenges? What if, following the precautionary principle, England had invested fortunes in odor elimination and not addressed water supplies? The Miasma Theory was the best theory they had. What would future generations think of them for not acting to clear the air? Now in retrospect, what would we have thought of them today for investing so many resources in a pointless endeavor?
Today we have issues like global warming. We're told there is incontrovertible evidence that CO2 is causing global warming, despite the fact climatology is still in its infancy. The correlation between CO2 and warming makes the conclusion self-evident. Only crackpots and shills for special interests would challenge these settled facts. The idea of CO2 destroying the planet dovetails nicely with our prejudices about evil corporations wantonly destroying the environment in the name of capitalism. Even if we're wrong, we must invoke the precautionary principle and invest trillions of dollars to stop CO2 production today. What will future generations think of us for not addressing problems when we could have?
In the case of cholera, the Londoners lucked out in that their solution to getting rid of the stench also altered the water supply for the better. They achieved a good solution through false understanding. What if it turns out that warming is overwhelmingly in response to the sun's radiation and the investment in CO2 reduction turns out to have been pointless? What if it turns out that warming is indeed a problem, but the cause lies elsewhere, and the CO2 correlation is insignificant? All these funds will have been diverted from curing AIDS, curing diseases, developing clean water, or eliminating poverty. How will future generations judge our actions?
My point is that there is risk involved in whichever option you choose. That is why open dialog without demonizing dissenters is essential to making good public policy. Prudence, not zeal or denial, must be the dominant mode of behavior.
Ghost Map is a wonderful illustration of how science and public policy interplay. It is a very well-written and thought-provoking book. I highly recommend it.
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