Infection depends on relationships. Without organisms (including people) that complete the chain of transmission, the microorganisms that cause disease would not be able to reproduce. Without sizeable host populations, diseases would die out quickly, blowing into oblivion like seeds of grass scattered on dry rock. When infectious diseases arrive in denser societies, however, they can grow to catastrophic size.
Some epidemics have left a particularly deep impression in human memory, whether because of their ferocious destruction or because of the ways in which they have been understood. Often, diseases have been seen as punishments, as manifestations of the will of God against those who have sinned. When this occurs -- as it has, over and over again in history -- the physical disease is accompanied by a social plague as well, one which can cause great suffering of its own.
The two most memorable diseases of the European Middle Ages were plague and leprosy. Leprosy was endemic, causing a slow and horrifying degeneration of the body. Plague, on the other hand, was a rapid murderer of millions. Caused by a bacillus, plague is transmitted by fleas that often infest rats and other rodents. Its most common symptoms include fever, severe headaches, delirium, prostration, and "buboes," extreme and painful swellings of the lymph nodes in the armpits and groin. Typically, people infected with plague die within eight days.
The most famous European outbreak of plague was called the "Black Death." Presumed to have begun in Central Asia, it was carried by ship-borne rats to Europe, and arrived in Milan in 1348. Within three years, the entire European world was devastated. In some areas, two-thirds to three-quarters of the population died -- perhaps as many as 25 million in all. This mortality tore society apart. The Italian author Giovanni Boccaccio wrote (in an early English translation) that "brother forsook brother, uncle nephew, and sister brother, and oftentimes wife husband. Nay (what is yet more extraordinary and well nigh incredible), fathers and mothers refused to visit or tend their very children, as [if] they had not been theirs."
People explained the Black Death in many ways -- almost all of them wrong. One common and insidious theory was that Jews had caused the plague by poisoning the wells from which urban populations drew their water. In response to this popular view, the officials of Basel, Switzerland, carried out the publicís desire for retribution by enclosing all the Jews in the city in a wooden structure and burning them to death. Plague remained a threat to Europe until the rats that carried the infected fleas were displaced by a different, less hospitable, breed.
Leprosy affected victims and communities in a different but equally frightening way. Far less infectious than plague, leprosy is caused by a bacterium (mycobacterium leprae) that eats through nerve endings, blood vessels, ligaments, skin tissue, and even bone. In the process, the hostís fingers and toes, face, and voice become deformed in ways that often horrify those who behold them. Societies have often taken these deformations as the visible signs of sin, and have therefore expelled lepers from their midst.
Religious horror of leprosy extends far back in the Judeo-Christian tradition. In Leviticus, for example, the Bible commands that the leper must shout out, "Unclean, unclean,"and solemnly condemns him to a life of utter solitude: "He shall dwell alone; without the camp shall his habitation be." Following this path, medieval Christianity also excluded the leper from society and viewed him or her as a person dead to the world. Thus a medieval ritual required the leper to stand in an open grave, while a priest pronounced this stern expulsion: "I forbid you ever to enter the church or monastery, fair, mill, market-place, or company of persons . . . ever to leave your house without your leperís costume . . . ever to touch children or give them anything." Sometimes this living death was packaged with the promise of speedy redemption in the life to come, but leprosy still remained powerfully and disturbingly tied to sin.
If leprosy and plague were the most striking diseases of the Middle Ages, they found jarring echoes in smallpox and syphilis, two epidemics of the Renaissance. While both smallpox and syphilis had existed before this time, it may have been the social developments of the era -- the Age of Exploration -- that catapulted them into international prominence. Smallpox, a disease of Europe and Asia, seems to have been unheard of in the Americas until European explorers landed there in the fifteenth century. It devastated the New World, killing as much as half the population. Some historians, in fact, have argued that it was smallpox, not the military prowess of the conquistadores, that allowed the conquest of the Americas. Meanwhile, syphilis was first recorded in Europe in 1493, immediately after Columbus and his sailors returned to Spain. (Medical historians still argue about whether the disease was imported from America or whether the timing was simply a coincidence.) Syphilis -- far more virulent and loathsome then than now: it was often called simply the Pox -- was the subject of intense and wide-ranging blame. The Russians called it the "Polish disease"; the Poles ascribed it to the Germans. To the Germans, the English, and the Italians, meanwhile, it was the morbus gallicus, the French disease. The French, however, laid the responsibility on the Neapolitans, the Dutch and Portuguese on the Spanish, and Japan on the Portuguese.
Regardless of its geographical origin, syphilis was pretty clearly tied to sex, both because it was common among groups of famously easy virtue (prostitutes and soldiers), and because its abscesses and rubbery tumors often first turned up on the genitals. As a result, the disease attracted a harsh opprobrium. The Spanish bishop Gaspare Torella, who was also physician to the papal court, publicly asked whether syphilitics even deserved to be cured. "Ought one to work against the will of God,"he asked,"who has punished them by the very means in which they had sinned?" Picking up the taint of leprosy (with which it was often associated -- ancient, deserted leper houses were sometimes turned into syphilis wards), syphilis was a magnet for horror, embarrassment, and blame.
There were other epidemics. Smallpox lashed Europe in a pandemic in 1614. Plague devastated London in 1665 and Marseilles in 1720; yellow fever terrorized Philadelphia, the new American capital, in 1793. These diseases too were often seen as punishment for sin of one kind or another -- even the "sin" of poverty. One seventeenth-century English writer voiced the disdain and disgust of the upper classes when he described bubonic plague as "a broom in the hands of the Almighty, with which he sweepeth the most nasty and uncomely corners of the universe."
The victims of cholera received the same cold shoulder in its four nineteenth-century pandemics. One of these tidal waves spread over most of the globe, beginning in India in 1826 and spreading over the next six years to Russia, Persia (now Iran), Europe, Britain, and North America. Like plague, cholera is easily transmitted among people living under unsanitary conditions: it is spread when food and water are contaminated with feces, which happened far too often in an era when indoor plumbing was a luxury enjoyed only by a few. Those afflicted suffer from severe cramps, vomiting, fever, dehydration, and sudden death; they can die within a day. And since cholera flourished among the ill-fed and ill-housed, the New York Times in 1866 described it as"the curse of the dirty, the intemperate, and the degraded."
People suffering from tuberculosis fared no better. Tuberculosis, or "consumption,"was the most devastating chronic disease of the nineteenth century. Though romanticized in stories such as Alexandre Dumas' Camille, tuberculosis is a wasting disease that caused great suffering -- fatigue, weight loss, chills, aches, fevers, and, most characteristically, a violent and even bloody cough. Like many diseases, TB most commonly affects people who live and work in crowded conditions and who suffer from malnutrition, such as the urban poor. Thus like plague, cholera, and other diseases, tuberculosis was linked with "dissolute and immoral" living. As a cure, patients (particularly the wealthy) were encouraged to take rest cures in mountain sanatoria or to take up active lifestyles in warmer, more salubrious climes. Women, however, were often encouraged by physicians to stay home and attend to their family responsibilities: though their disease was the same, women's health was subordinated to their role in society. Only in 1882, when Robert Koch discovered that tuberculosis is caused not by weakness or moral decay, did the disease's many stereotypes begin to fade away.
Epidemics continued to claim lives in huge numbers in the early twentieth century -- particularly the "Spanish flu" pandemic of 1918. Influenza struck Chungking in July, Persia in early August, and France two weeks later. By the end of two months it had covered the entire globe. Twenty-two million people perished (half a million in the U.S., twelve million in India) -- nearly twice as many as had died in all of World War I. Several decades later, the U.S. and other countries were attacked by waves of polio. Polio affected far fewer people than the 1918 flu, but it often caused panic because it primarily affected children, whom it could paralyze and even kill. In the U.S., as many as 40,000 children a year were affected in the early 1950s. These figures have dropped dramatically in Western nations, as a result of the Salk and Sabin vaccines. In developing countries, however, vaccine use is still sporadic, and polio remains a danger, particularly in India and Africa.
From the 1950s to the 1970s, it seemed that the age of the epidemic was over, at least in the developed world. Vaccines had reduced polio to a rare event and, by 1979, had totally eradicated smallpox. Antibiotics, too, seemed to offer a cure for every infection. Starting in the 1940s with penicillin, antibiotics proved effective against a broad range of previously incurable bacterial diseases, including pneumonia, tuberculosis, meningitis, diphtheria, syphilis, gonorrhea, and plague. Predictions of another influenza epidemic in 1976 proved false, and this event only reinforced the view that, in the years ahead, the major remaining challenge for Western medicine was that of chronic illnesses like heart disease and cancer.
More recent events, however, proved that this optimism was tragically mistaken. AIDS brought this fact home to Americans in the 1980s, but in fact plenty of evidence had been available before. Cholera epidemics ravaged Asia in the 1960s and the Middle East, Africa, and the Soviet Union a decade later. Plague broke out in India in 1995. Other diseases once considered vanquished returned in new, drug-resistant strains to pose serious threats to world health, malaria and tuberculosis among them. In addition, recent decades have seen the discovery of terrifying new infectious diseases. Marburg fever (1967), Lassa fever (1969), Ebola (1976), and of course AIDS. These new diseases are highly contagious; many of them attack and kill very quickly; and they destroy the human body in ferocious ways. Reflecting the sudden shift in world-view that these new infections have changed, writer Susan Sontag has described the future as "not 'Apocalypse Now' but 'Apocalypse From Now On.'"
There is no question about it: epidemic diseases make the world a dangerous place. In order to fight against them, humanity must address every aspect of their spread: the pathogens themselves, the behavior of individuals, and the society and environment in which micro-organisms and humans interact. Unless the fight is waged on all three of these fronts, it is extremely difficult to protect the public health. Physicians and researchers can develop and administer drugs; individuals must act responsibility to safeguard themselves and others. But, in addition, society must provide a context in which health is a first priority. Humanity must learn from experience that diseases like leprosy, cholera, and AIDS are not signs of moral failure or divine punishment, but a permanent part of life. Until this happens, the social and medical history of the future can represent no progress over the often painful history of the human past.
Peter Lewis Allen, Ph.D. is author of The Wages of Sin: Sex and Disease, Past and Present (University of Chicago Press, 2000), which was highlighted as part of the Body Positive Book Reading Club in the December 2000 issue.