Notes – Epidemics and Society: From the Black Death to the Present
by – Frank M. Snowden
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This hypothesis is that epidemics are not an esoteric subfield for the interested specialist but instead are a major part of the “big picture” of historical change and development. Infectious diseases, in other words, are as important to understanding societal development as economic crises, wars, revolutions, and demographic change.
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Spontaneous public responses: Under certain circumstances the passage of epidemic disease through communities has triggered large-scale and revealing responses among those at risk. These responses include stigmatization and scapegoating, flight and mass hysteria, riots, and upsurges in religiosity.
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1969 the US Surgeon General experienced a premature surge of optimism in the power of science and public health to combat microbes, declaring the end of the era of infectious diseases. During the same era of exuberant hubris, international public health authorities announced that it would be possible by the end of the twentieth century to eradicate one microbial threat after another, beginning with malaria and smallpox. In this triumphant climate, schools of medicine such as Yale and Harvard closed their departments of infectious diseases.Well into the twenty-first century smallpox remains the only disease to have been successfully eradicated. Worldwide, infectious diseases remain leading causes of death and serious impediments to economic growth and political stability. Newly emerging diseases such as Ebola, Lassa fever, West Nile virus, avian flu, Zika, and dengue present new challenges, while familiar afflictions such as tuberculosis and malaria have reemerged, often in menacing drug-resistant forms. Public health authorities have particularly targeted the persisting threat of a devastating new pandemic of influenza such as the “Spanish lady” that swept the world with such ferocity in 1918 and 1919.
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Indeed, many of the central features of a global modern society continue to render the world acutely vulnerable to the challenge of pandemic disease. The experiences of SARS and Ebola—the two major “dress rehearsals” of the new century—serve as sobering reminders that our public health and biomedicine defenses are porous. Prominent features of modernity—population growth, climate change, rapid means of transportation, the proliferation of megacities with inadequate urban infrastructures, warfare, persistent poverty, and widening social inequalities—maintain the risk. Unfortunately, not one of these factors seems likely to abate in the near futureA final important theme of Epidemics and Society is that epidemic diseases are not random events that afflict societies capriciously and without warning. On the contrary, every society produces its own specific vulnerabilities. To study them is to understand that society’s structure, its standard of living, and its political priorities. Epidemic diseases, in that sense, have always been signifiers, and the challenge of medical history is to decipher the meanings embedded in them.
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This is because plague is nearly everyone’s candidate as the worst-case scenario for epidemic disease. The word “plague” is virtually synonymous with terror. It was an extraordinarily rapid and excruciating killer, whose symptoms were dehumanizing. Furthermore, in the absence of an effective treatment, a substantial majority of its sufferers died, ensuring that contemporaries feared the destruction of entire populations of major cities such as London and Paris. Here was the foundation for the horrifying cliché about plague—that too few people survived to bury the dead.
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Bubonic plague is the inescapable reference point in any discussion of infectious diseases and their impact on society. In many respects plague represented the worst imaginable catastrophe, thereby setting the standard by which other epidemics would be judged.
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Other fearful characteristics of this disease were the age and class profiles of its victims. Familiar endemic diseases primarily strike children and the elderly. This is the normal experience of a community with infectious diseases such as mumps, measles, smallpox, and polio. But the plague was different: it preferentially targeted men and women in the prime of life. This aspect made plague seem like an unnatural or supernatural event. It also magnified the economic, demographic, and social dislocations that it unleashed. In other words, plague left in its wake vast numbers of orphans, widows, and destitute families. Furthermore, unlike most epidemic diseases, the plague did not show a predilection for the poor. It attacked universally, again conveying a sense that its arrival marked the final day of reckoning—the day of divine wrath and judgment.
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A major task of our exploration of plague is to examine why such major differences exist in the realm of infectious diseases—why some leave a major cultural, political, and social imprint, and others do not.
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Infectious diseases are normally placed along a continuum according to their severity in terms of the numbers of sufferers and the extent of their geographical reach. An “outbreak” is a local spike in infection, but with a limited number of sufferers. An “epidemic,” by contrast, normally describes a contagious disease that affects a substantial area and a large number of victims. Finally, a “pandemic” is a transnational epidemic that affects entire continents and kills massive numbers of people. All three terms, however, are loose approximations, and the boundaries separating one from another are imprecise and sometimes subjective. Indeed, a contagious disease confined to a single locality is occasionally termed a pandemic if it is sufficiently virulent to afflict nearly everyone in the area.
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In accordance with this terminology, humanity has experienced three pandemics of bubonic plague. Each consisted of a cycle of recurring epidemic waves or visitations, and the cycle lasted for generations or even centuries.
The cyclical pattern of plague was marked also by a pronounced seasonality. Plague epidemics usually began in the spring or summer months and faded away with the coming of colder weather. Especially favorable were unusually warm springs followed by wet, hot summers. The modern explanations for these propensities are the need of fleas, which carried the disease, for warmth and humidity to enable their eggs to mature, and the inactivity of fleas in cold and dry conditions. Although this pattern predominated, the disease has also been known to erupt mysteriously in Moscow, Iceland, and Scandinavia in the depth of winter. These atypical eruptions of the disease posed serious epidemiological puzzles.
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Epidemic diseases are not simply transposable causes of suffering and death. On the contrary, the history of each high-impact infectious disease is distinct, and one of the major variables is the specific manner in which it affected its victims. Indeed, a feature of bubonic plague was that its symptoms seemed almost purposefully designed to maximize terror; they were excruciating, visible, dehumanizing, and overwhelming.
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Plague hospitals suffered the disadvantage of admitting large numbers of patients at an advanced stage of illness, and frequently the sheer numbers of victims overwhelmed the staff. On many occasions patients died or recovered without receiving medical attention or treatment of any kind.
Everywhere, major epidemics caught authorities unprepared, leading to confusion, chaos, and improvisation. Even the best-run lazarettos lacked the capacity to cope with the sudden caseload of a plague emergency.
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Thus a city besieged by a major plague epidemic became a perfect dystopia. Bonds of community and family ties were severed. Religious congregations found their churches bolted, sacraments unavailable, and bells silent. Meanwhile, economic activity halted, shops closed, and employment ceased, increasing the threat of hunger and economic ruin. The political and administrative practices of normal life did not survive as authorities fell seriously ill, died, or fled. Worst of all, above every other concern towered the menace of sudden and painful death made vivid by the stench in the streets and the dying sufferers who often lived out their final anguish in public.
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Plague regulations also cast a long shadow over political history. They marked a vast extension of state power into spheres of human life that had never before been subject to political authority. One reason for the temptation in later periods to resort to plague regulations was precisely that they provided justification for the extension of power, whether invoked against plague or, later, against cholera and other diseases. They justified control over the economy and the movement of people; they authorized surveillance and forcible detention; and they sanctioned the invasion of homes and the extinction of civil liberties. With the unanswerable argument of a public health emergency, this extension of power was welcomed by the church and by powerful political and medical voices. The campaign against plague marked a moment in the emergence of absolutism, and more generally, it promoted an accretion of the power and legitimation of the modern state.
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one goal of this book is to examine the influence of different types of infectious diseases. Each is a distinctive and special case with its own mechanisms and its own historical impact; therefore, it is important to think comparatively.
What is the causative pathogen of the disease? Bubonic plague, as we know, was caused by the bacterium Yersinia pestis. As we move forward we will encounter three different categories of microbial pathogens: bacteria, viruses, and plasmodia. In a medical course on infectious diseases we would also have to consider prions, which cause such diseases as “mad cow disease” and kuru; but here, the diseases we consider are all bacterial, viral, or plasmodial. 2. What is the total mortality and morbidity of the epidemic? “Mortality” indicates the total number of deaths, and “morbidity” the total number of cases, both fatal and nonfatal. Clearly, the numbers of deaths and cases are one of the measures of the impact of an epidemic. These statistics, for example, provide some support for the argument that Spanish influenza, which caused perhaps 50 million deaths in 1918–1919, was a more significant event than the 1995 outbreak of Ebola at Kikwit in the Democratic Republic of the Congo. For all of its international high drama at the time, the Ebola epidemic caused “only” 250 deaths and 315 cases, and it has left a slender legacy. On the other hand, mortality and morbidity figures are no more than a first and coarse assessment of historical significance, which can be established only by detailed case-by-case analysis that is as much qualitative as quantitative. It would be morally desensitizing and historically wrong-headed, for instance, to conclude a priori that by the measure of total mortality only major catastrophes such as those created by bubonic plague and Spanish influenza are important events. Indeed, one can argue forcefully that epidemics on a far smaller scale, such as outbreaks of Asiatic cholera in which “only” a few thousand perished, were decisive occurrences that cast a long historical shadow. There is no simple “quick fix” to the problem of weighing historical influence. But morbidity and mortality count in the scale and need to be considered. 3. What is the case fatality rate (CFR) of the disease? This question addresses the virulence of the pathogen. CFR is determined by mortality as a proportion of morbidity—or, to put it another way, the percentage of cases that end in death. CFR is therefore the “kill rate” of a disease. One of the reasons that bubonic plague caused such terror and disruption was its exceptionally high CFR, which varied from 50 to 80 percent. At the other extreme, the great Spanish influenza that accompanied the end of the First World War gave rise to an unparalleled morbidity, but it had a low CFR. This difference is important in assessing the variation in the popular responses to the two diseases. 4. What is the nature of the symptoms of the disease? Symptoms that are particularly painful or degrading in terms of the norms of the society that experiences the affliction—such as those associated with plague, smallpox, and cholera, for instance—can contribute to how the disease is experienced and assessed.… Somes have been hidden or truncated due to export limits.
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Since smallpox is our first viral disease, we need to clarify our terminology and to note a biological distinction. “Microbe” is a general term for microscopic organisms, and it includes both bacteria such as Y. pestis and viruses such as variola major. Bacteria are unicellular organisms that are definitely and unequivocally forms of life. They contain DNA, plus all of the cellular machinery necessary to read the DNA code and to produce the proteins required for life and reproduction. Viruses are completely different, but there is a possible source of confusion lurking for the student of medical history. The word “virus” is ancient. In the humoral system, diseases, as we know, were seen to arise as a result of assaults on the body from outside. One of the major environmental factors leading to disease was believed to be corrupted air, or miasma. But another important cause was a poison that was no more clearly identified than “miasma” and was termed a “virus.” So when bacteria were first discovered in the late nineteenth century, they were commonly considered to be a form of virus. When a distinct category of microbes was discovered—the one that modern-day usage terms “viruses”—they were at first designated as “filterable viruses,” meaning that they could pass through filters that were fine enough to retain bacteria. For the remainder of this book, the term “virus” will be reserved for these tiny filterable microbes that are parasitic particles some five hundred times smaller than bacteria. Elegant scientific experiments established their existence by 1903, but they were not actually seen until the invention of the electron microscope in the 1930s, and their biological functioning was not understood until the DNA revolution of the 1950s. Viruses consist of some of the elements of life stripped to the most basic. A virus is nothing more than a piece of genetic material wrapped in a protein case or, in the definition of the Nobel Prize–winning biologist Peter Medawar, “a piece of nucleic acid surrounded by bad news.”1 Viruses are not living cells but cell particles that are inert on their own. They contain a small number of genes. A smallpox virus, for instance, may contain two hundred to four hundred genes, as opposed to the twenty thousand to twenty-five thousand genes found in a human being. Thus streamlined, viruses lack the machinery to read DNA, to make proteins, or to carry out metabolic processes. They can do nothing in isolation, and they cannot reproduce. Viruses survive as microparasites that invade living cells. Once inside a cell, they shed their protein envelope and release their nucleic acids into the cell. The genetic code of the virus (and the virus is almost nothing more) hijacks the machinery of the cell, giving it the message to produce more viral progeny. In this way the virus transforms living cells into virus-producing factories. In the process the viruses destroy the host cells they have invaded. The newly formed mature… Somes have been hidden or truncated due to export limits.
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Furthermore, since inoculation resulted in actual smallpox, there was always the possibility that it would set off a wider outbreak or even unleash an epidemic. For precisely that reason a Smallpox and Inoculation Hospital was opened in London with the twofold purpose of caring for people who had been inoculated and isolating them until they were no longer infectious and a potential hazard to the community. Thus inoculation was always surrounded by a spirited debate as to whether, on balance, it saved more lives than it destroyed.
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Those who asserted the doctrine of the conquest of infection viewed the microbial world as largely static or only slowly evolving. For that reason there was little concern that the victory over existing infections would be challenged by the appearance of new diseases for which humanity was unprepared and immunologically naive. Falling victim to historical amnesia, they ignored the fact that the past five hundred years in the West had been marked by the recurrent appearance of catastrophic new afflictions—for instance, bubonic plague in 1347, syphilis in the 1490s, cholera in 1830, and Spanish influenza in 1918–1919.
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Burnet was typical. He was a founding figure in evolutionary medicine who acknowledged, in theory, the possibility that new diseases could arise as a result of mutation. But in practice he believed that such appearances are so infrequent as to require little concern. “There may be,” he wrote, “some wholly unexpected emergence of a new and dangerous infectious disease, but nothing of the sort has marked the last fifty years.”5 The notion of “microbial fixity”—that the diseases we have are the ones that we will face—even underpinned the International Health Regulations adopted worldwide in 1969, which specified that the three great epidemic killers of the nineteenth century—plague, fever, and cholera—were the only diseases requiring “notification.” Notification is the legal requirement that, when diagnosed, a given disease be reported to national and international public health requirements. Having framed notification in terms of a short list of three known diseases, the regulations gave no thought to what action would be required if an unknown but deadly and transmissible new microbe should appear.
belief in the stability of the microbial world was one of the articles of faith underpinning the eradicationists’ vision, a second misplaced evolutionary idea also played a role. This was the doctrine that nature is fundamentally benign because, over time, the pressure of natural selection drives all communicable diseases toward a decline in virulence. The principle was that excessively lethal infectious diseases would prevent their own transmission by prematurely destroying their hosts. The long-term tendency, the proponents of victory asserted, is toward commensalism and equilibrium. New epidemic diseases are virulent almost by accident as a temporary maladaptation, and they therefore evolve toward mildness, ultimately becoming readily treatable diseases of childhood. Examples were the evolution of smallpox from variola major to variola minor, the transformation of syphilis from the fulminant “great pox” of the sixteenth century into the slow-acting disease of today, and the transformation of classic cholera into the far milder El Tor serotype.
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Memory of the power of public health and science provided impetus to the overconfidence of the transitionists, but forgetfulness also contributed. The idea—expressed by Surgeon General William H. Stewart in 1969—that the time had come to “close the book on infectious diseases” was profoundly Eurocentric. Even as medical experts in Europe and North America proclaimed victory, infectious diseases remained the leading cause of death worldwide, especially in the poorest and most vulnerable countries of Africa, Asia, and Latin America. Tuberculosis was a prominent reminder. Sanatoria were closing their doors in the developed North, but TB continued its ravages in the South; and it continued to claim victims among the marginalized of the North—the homeless, prisoners, intravenous drug users, immigrants, and racial minorities. As Paul Farmer has argued in his 2001 book Infections and Inequalities: The Modern Plagues, tuberculosis was not disappearing at all: the illusion persisted only because the bodies it affected were either distant or hidden from sight. Indeed, conservative WHO estimates suggested that in 2014 there were approximately as many people ill with tuberculosis as at any time in human history. WHO also reported that in 2016, 10.4 million people fell ill with tuberculosis and that 1.7 million died of it, making TB the ninth leading cause of death worldwide and the top cause of death from infectious diseases, ahead of HIV/AIDS.
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An important reason for this new vulnerability was the legacy of eradicationism itself. The belief that the time had come to close the books on infectious diseases had led to a pervasive climate that critics labeled variously as “complacency,” “optimism,” “overconfidence,” and “arrogance.” The conviction that victory was imminent had led the industrial world to premature and unilateral disarmament. Assured by a consensus of the leading medical authorities for fifty years that the danger was past, federal and state governments in the United States dismantled their public health programs dealing with communicable diseases and slashed their spending; investment by private industry on the development of new vaccines and classes of antibiotics dried up; the training of health-care workers failed to keep abreast of new knowledge; vaccine development and manufacturing were concentrated in a few laboratories; and the discipline of infectious diseases no longer attracted its share of research funds and the best minds. At the nadir in 1992, the US federal government allocated only $74 million for infectious disease surveillance as public health officials prioritized other vital concerns, such as chronic diseases, tobacco use, geriatrics, and environmental degradation. For these reasons, informed assessments of American preparedness to face the unexpected challenges of emerging contagious diseases were disheartening.
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Similarly, but more bluntly, Michael Osterholm, the Minnesota state epidemiologist, informed Congress in 1996: “I am here to bring you the sobering and unfortunate news that our ability to detect and monitor infectious disease threats to health in this country is in serious jeopardy. . . . For twelve of the States or territories, there is no one who is responsible for food or water-borne disease surveillance. You could sink the Titanic in their back yard and they would not know they had water.”17 Lederberg and other theorists of emerging and reemerging diseases developed a critique of eradicationist hubris that went deeper than a mere protest against a decline in vigilance. They argued that, unnoticed by the eradicationists, society since World War II had changed in ways that actively promoted epidemic diseases. One of the leading features most commonly cited was the impact of globalization in the form of the rapid mass movement of goods and populations. As William McNeill noted in Plagues and Peoples (1976), the migration of people throughout history has been a dynamic factor in the balance between microbes and humans. Humans are permanently engaged in a struggle in which the social and ecological conditions that they create exert powerful evolutionary pressure on microparasites. By mixing gene pools and by providing access to populations of nonimmunes, often in conditions under which the microbes thrive, globalization gives microorganisms a powerful advantage. In the closing decades of the twentieth century, the speed and scale of globalization amounted to a quantum leap as the number of passengers boarding airplanes alone surpassed 2 billion a year. Elective air travel, however, was only part of a far larger phenomenon. In addition there are countless involuntary immigrants and displaced persons in flight from warfare, famine, and religious, ethnic, or political persecution. For Lederberg and the IOM, these rapid mass movements decisively tilted the advantage in favor of microbes, “defining us as a very different species from what we were 100 years ago. We are enabled by a different set of technologies. But despite many potential defenses—vaccines, antibiotics, diagnostic tools—we are intrinsically more vulnerable than before, at least in terms of pandemic and communicable diseases.”18 After globalization, the second factor most frequently underlined is demographic growth, especially since this growth so often occurs in circumstances that are the delight of microorganisms and the insects that transmit them. In the postwar era, populations have soared above all in the poorest and most vulnerable regions of the world and in cities that lack the infrastructure to accommodate the influx. The global urban population is currently soaring at four times the rate of the rural population, creating sprawling and underserved megacities with more than 10 million inhabitants. By 2017 there were forty-seven such conurbations, such as Mumbai in India, Lagos… Somes have been hidden or truncated due to export limits.
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infectious diseases that do not depend on the mobility of their host for transmission (because they are borne by vector, water, or food) are under no selective pressure to become less virulent; (2) overpopulated and unplanned urban or periurban slums provide ideal habitats for microbes and their arthropod vectors; and (3) modern transportation and the movements of tourists, migrants, refugees, and pilgrims facilitate the process by which microbes and vectors gain access to these ecological niches.
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theorists of emerging diseases argue that antibiotics are a “nonrenewable resource” whose duration of efficacy is biologically limited. By the late twentieth century, this prediction was reaching fulfillment. At the same time as the discovery of new classes of antimicrobials had slowed to a trickle, the pharmaceutical marketplace staunched the flow by inhibiting research on medications that are likely to yield low profit margins. Competition, regulations mandating large and expensive clinical trials, and the low tolerance for risk of regulatory agencies all compound the problem.
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while antimicrobial development stagnates, microorganisms have evolved extensive resistance. As a result, the world stands poised to enter a post-antibiotic era. Some of the most troubling examples of the emergence of resistant microbial strains are plasmodia that are resistant to all synthetic antimalarials, S. aureus that is resistant both to penicillin and to methicillin (MRSA), and strains of Mycobacterium tuberculosis that are resistant to first-line medications (MDR-TB) and to second-line medications (XDR-TB). Antimicrobial resistance threatens to produce a global crisis, and many scientists anticipate the appearance of strains of HIV, tuberculosis, S. aureus, and malaria that are not susceptible to any available therapy.
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the concept of emerging and reemerging diseases was intended to raise awareness of the most important threat of all—that the spectrum of diseases that humans confront is broadening with unprecedented rapidity. The number of previously unknown conditions that have emerged to afflict humanity since 1970 exceeds forty, with a new disease discovered on average more than once a year. The list includes HIV, Hantavirus, Lassa fever, Marburg fever, Legionnaires’ disease, hepatitis C, Lyme disease, Rift Valley fever, Ebola, Nipah virus, West Nile virus, SARS, bovine spongiform encephalopathy, avian flu, Chikungunya virus, norovirus, Zika, and group A streptococcus—the so-called flesh-eating bacterium. Skeptics argue that the impression that diseases are emerging at an accelerating rate is misleading. Instead, they suggest, it is largely an artifact of heightened surveillance and improved diagnostic techniques. WHO has countered that not only have diseases emerged at record rapidity, as one would expect from the transformed social and economic conditions of the postwar world, but that they gave rise between 2002 and 2007 to a record eleven hundred worldwide epidemic “events.” A careful examination of the question, published in Nature in 2008, involved the study of 335 emerging infectious disease (EID) events between 1940 and 2004, controlling for reporting effort through more efficient diagnostic methods and more thorough surveillance. The study concluded: “The incidence of EID events has increased since 1940, reaching a maximum in the 1980s. . . . Controlling for reporting effort, the number of EID events still shows a highly significant relationship with time. This provides the first analytical support for previous suggestions that the threat of EIDs to global health is increasing.”21
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In the stark words of the US Department of Defense, “Historians in the next millennium may find that the 20th century’s greatest fallacy was the belief that infectious diseases were nearing elimination. The resultant complacency has actually increased the threat.
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