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Encarta Historical Essays reflect the knowledge and insight of leading historians and researchers. This collection of essays is assembled to support the National Standards for World History. In this essay, Christopher King traces the effects of plague and scientists’ gradual understanding of the devastating disease.
By Christopher King
The study of the incidence and spread of disease in large populations is called epidemiology. To control a disease, it is important to understand its source and how it spreads. Modern epidemiologists, for example, are trying to understand the origins and the spread of b human immunodeficiency virus (HIV), the virus that causes acquired immune deficiency syndrome (AIDS). They hope to one day manage and possibly even cure this deadly disease. However, understanding the nature of a disease is a difficult task, even using the latest tools of microbiology and molecular genetics. Imagine how difficult it was, then, hundreds of years ago, when medical knowledge had advanced little beyond superstition. At that time, the task of understanding a merciless disease must have seemed impossible.
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Such was the case with the great epidemics of plague that have raged throughout history. During the Middle Ages (around the 5th century to the 15th century), the word plague was used indiscriminately to describe epidemic illnesses; today, the term is applied specifically to an acute, infectious, contagious disease of rodents and humans caused by a form of bacteria. We know today that bubonic plague, the most well-known type of the disease, is transmitted by the bite of a parasitic insect. Another form, pneumonic plague, is mostly transmitted by droplets sprayed by the mouth and nose of infected persons. Septicemic plague, still another form, can be spread by direct contact with contaminated hands. However, during the mid-1300s, when the disease eventually called the Black Death wiped out as much as one-third of Europe’s population, doctors and scientists were at a loss to find its cause, much less a cure.
Unable to explain or comprehend the magnitude of the suffering, some observers could only record the devastation caused by the disease. Eyewitness descriptions of the plague date back to the year 541, when plague broke out in the city of Constantinople (now İstanbul, Turkey), then part of the Byzantine empire. Procopius, who was the historian to the court of Emperor Justinian I, describes an epidemic during which 'the whole human race came near to being annihilated.' In Procopius’ accounts, the symptoms of plague began with 'a sudden fever.' For a brief period, there was no sign of inflammation or changes in skin color. 'But on the same day in some cases, in others on the following day, and in the rest not many days later,” Procopius wrote, “a bubonic swelling developed; and this took place not only in the particular part of the body which is called the groin, that is, below the abdomen, but also inside the armpits, and in some cases besides the ears, and at different points on the thighs came a large swelling or bubo.'
Procopius noted that some victims fell into a coma, while others were seized with a 'violent delirium,' being convinced that 'men were coming upon them to destroy them.' Some victims had to be prevented from rushing out of their houses, or attempting to drown themselves, or trying to jump from a great height. As Procopius continues, 'And in those cases where neither coma nor delirium came on, the bubonic swelling became mortified and the sufferer, no longer able to endure the pain, died. Death came in some cases immediately, in others after many days.' This so-called 'Plague of Justinian,' named after the Byzantine emperor, raged in Constantinople until the spring of 542. It killed as many as 200,000 people, or 40 percent of the city's population.
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Eight centuries later, the Black Death swept through Europe, reaching Italy in 1347. The Italian writer Giovanni Boccaccio, in his classic work The Decameron, describes cases of the plague in Florence: 'At the onset of the disease, both men and women were affected by a sort of swelling in the groin or armpits, which sometimes attained the size of a common apple or egg. Some of these swellings were larger and some were smaller, and all were commonly called boils. From these two starting points the boils began in a little while to spread and appear generally all over the body. Afterwards, the manifestations of the disease changed into black or lurid spots on the arms, the thighs and the whole person.' Today, historians estimate that perhaps one-third of Florence's 80,000 inhabitants died between the spring and summer of 1348.
Vivid descriptions of the plague also come from the Great Plague of London, an outbreak that occurred in 1665. Such descriptions were recorded by English writer Daniel Defoe in A Journal of the Plague Year (1722), his reconstruction of the disaster. Describing the speed and cruelty with which the disease struck, Defoe tells the story of one young woman who falls ill with vomiting and 'a violent pain in the head.' Her mother performs an examination and confirms the worst: 'looking upon her body with a candle, immediately discovered the fatal tokens on the inside of her thighs. Her mother not being able to contain herself, threw down her candle, and shrieked out in such a frightful manner, that it was enough to place horror upon the stoutest heart in the world. As to the young maiden, she was a dead corpse from that moment; for the gangrene which occasions the spots had spread [over] her whole Body, and she died in less than two hours.' Elsewhere in his book, Defoe describes a city undergoing a nightmare of suffering: 'The pain of the swelling was in particular very violent, and to some intolerable.' People ran mad in the streets, 'raving and distracted, oftentimes laying violent hands on themselves, throwing themselves out at their windows, shooting themselves, mothers [murdering] their own children in their lunacy.'
Adding to the misery and terror of plague epidemics was ignorance; no one had any idea of the cause of the disease or its true means of transmission. Many people correctly believed that the contagion could be passed by breath—although during the Black Death one physician even proposed that a look from a dying man was enough to transmit a fatal infection. Accurate medical knowledge regarding the plague was centuries away. The plague-causing bacteria, and the process of its transmission to humans through infected rodents and fleas, would not be identified and understood until the 1890s. During the Black Death, most people viewed the plague as divine punishment for the sins of humanity. Doctors and scholars, meanwhile, produced whatever theories they could to explain the origin of the disease and to recommend curative or preventive measures.
According to one view, the causes were astrological: an unusual alignment of the planets Saturn, Jupiter, and Mars had caused a corruption of the atmosphere. Other theorists blamed earthquakes and other natural disasters for releasing foul air from the Earth's interior. This idea of corrupted, foul air—a miasma—was central to many theories about the plague's cause. Many preventive measures, therefore, hinged on counteracting or purifying corrupted air. For instance, woods such as juniper and ash were burned to create pleasant smells. The floors of houses were washed with rose water and vinegar. Recommended dietary supplements to ward off plague included myrrh, saffron, and pepper, along with servings of onions, garlic, and leeks. Defoe's observations in A Journal of the Plague Year indicate that preventive medicine in the 1660s had not improved much during the three centuries since the Black Death. Defoe writes of men holding garlic in their mouths and of a woman stuffing vinegar up her nose. Quacks of every description also advertised their wares on posters, promising antipestilential pills and other antidotes.
Today epidemiologists believe that the Black Death was most likely plague in its pneumonic form, infecting the lungs and spreading from person to person through sneezing or coughing. And while people in the Middle Ages did not understand how the disease was spread, its contagiousness was frightfully clear. Eyewitnesses describe this fear: 'Soon men hated each other so much that, if a son was attacked by the disease, his father would not tend him,' wrote a friar, describing the course of the Black Death in Messina, Sicily. 'If, in spite of all, he dared to approach him, he was immediately infected and … was bound to expire within three days.' An 8th-century historian, describing an earlier outbreak in Italy, records a similar erosion of family bonds in the face of raging plague: 'Sons fled, leaving the corpses of their parents unburied; parents forgetful of their duty abandoned their children in raging fever.' Another eyewitness to the Black Death wrote: 'Father abandoned child, wife husband, one brother another … none could be found to bury the dead for money or friendship ... they died by the hundreds, both day and night, and all were thrown in ditches and covered with earth. And as soon as those ditches were filled, more were dug. And I, Agnolo di Tura ... buried my five children with my own hands.'
During the Middle Ages, the actual treatment of plague often consisted of opening a victim's veins and drawing blood in order to release the infection. Another curative procedure was to attempt to open the swollen buboes and sterilize them by burning. Afterward, doctors applied various substances, such as the roots of white lilies or a plaster made from gum resin, to drain the poison. Again, the practice in Defoe's day seemed little changed from medieval procedures: 'The swellings in some grew hard, and they applied violent drawing plasters, or poultices, to break them; and if these did not do, they cut and scarified them in a terrible manner.' Such measures, as one observer noted, often put the patients 'to more pain than the disease did.' Still, as Defoe recounted, 'if the swellings could be brought to a head, and to break and run the patient generally recovered.'
Although it took centuries, medical science finally caught up with the disease. In 1894 a plague epidemic broke out in the Yunnan Province of China. Alexander Yersin, a 31-year-old Swiss pathologist who had traveled extensively in Indochina, arrived in Hong Kong hoping to identify the plague organism. Within seven weeks, he had succeeded in isolating and describing the bacterium. 'It seemed logical to start by first looking for a microbe in the blood of patients and in the pulp of the buboes,' he wrote in a letter. 'The pulp of the buboes always contain masses of short, stubby bacilli … Sometimes the bacilli seem to be surrounded by a capsule. One can find them in large numbers in the buboes and the lymph nodes of the diseased persons.' Yersin had discovered the plague-causing microbe that now bears his name: Yersinia pestis. A Japanese scientist, Shibasaburo Kitasato, identified the pathogen at around the same time and is usually credited as its codiscoverer.
Four years after Yersin's discovery, however, it was not yet known how the plague infection was spread. Some scientists believed that dust contaminated with plague bacteria from the fecal material of infected humans and rodents might be to blame. Victims, according to this scenario, admitted the bacteria by inhaling the dust, or by having it enter through a wound on the skin. The mystery was finally solved by French scientist Paul-Louis Simond during a plague outbreak in India in 1898. Simond, skeptical of previous theories, noted that examinations of many plague victims showed that they each had a small skin blister filled with the plague bacilli. Simond correctly surmised that this was the bite mark of an infected flea, such as Xenopsylla cheopis or Nosopsylla fasciatus. Ordinarily, these fleas infect rats and other burrowing mammals. In times of opportunity or necessity, however, human hosts will do. As scientists now know, the bite of a flea infected with the Y. pestis bacilli will transmit the infection from a flea to a human being.
Scientists now have a clear picture of bubonic plague: once inside the human body, the bacteria multiply rapidly, doubling their numbers every two hours as they circulate in the blood and lymphatic vessels. Although the body's immune system kills some of the bacteria, many survive even after being surrounded by immune-system cells. Inside the cells, the bacilli continue to multiply, producing offspring that are resistant to phagocytosisthat is, being ingested and destroyed by immune cells. The bacteria emit toxins that produce inflammatory damage in the lymph nodes, spleen, liver, and other organs, killing tissue and causing internal bleeding. Without treatment, death results from the massive bacterial growth.
The good news is that modern knowledge of the plague bacteria ultimately brought modern treatments of the disease. Diagnosed promptly, plague can be treated and cured with antibiotics such as streptomycin and tetracycline. The first plague vaccine was developed in 1896. The disease now occurs mostly in rural areas in developing nations—for example, an outbreak in India in 1994 was the last significant episode. However, there are occasional cases of human plague in the western and southwestern United States when people come into contact with infected mammals. Seven such cases, for example, were reported in 1995.
Scholars still debate some aspects of the great Black Death epidemic of the 14th century. Even the name itself has been subject to some speculation: the term Black Death is said to refer to the discolored skin of plague victims, the result of internal bleeding and dead tissue. However, there is no evidence that the term was used during the 1300s at the time of the great epidemic—indeed, the name Black Death was not applied to the epidemic until two or more centuries later. Rather, Europeans at the time referred to the epidemic as 'The Great Dying.' The exact origins of the term Black Death remain mysterious.
Some of the medical lore surrounding the plague has long been said to survive in an unlikely place: a children's rhyme. 'Ring Around the Rosy,' which is sometimes said to date from the London plague of 1665 or even from the 14th century Black Death, apparently refers to plague symptoms and treatments:
Ring around the rosy, pocket full of posies, ashes ashes, we all fall down.
According to popular interpretations, the 'rosy ring' corresponds to the purplish skin marks on plague victims, resulting from internal bleeding caused by the plague bacteria. A 'pocketful of posies' supposedly represents the herbs and spices carried to purify the air. 'Ashes' is alternately interpreted as a variant on 'achoo,' the sound of a sneeze signaling respiratory failure and the spreading of plague germs; the ashes from a fire lit to keep the plague at bay; or even the ashes of cremated plague victims. 'We all fall down,' of course, represents people literally falling dead under the onslaught of the plague.
Despite the rhyme's enduring reputation as a historical remnant of the plague, however, scholars of folklore have their doubts. As folklorist Philip Hiscock has noted, there is no evidence that 'Ring Around the Rosy' existed before the 1880s, a period that produced many different versions of the rhyme—none of them suggesting the plague in any way. Skeptical folklorists argue that the verse was a simple nonsense accompaniment to a children's dancing game in the 1800s. The plague interpretation, skeptics say, was invented after the fact and has been passed from generation to generation because it sounds so plausible.
Even the more scientific aspects of the plague are still debated. Some scholars, for example, have theorized that the epidemic that swept through Europe in the 14th century might not have been exclusively bubonic plague and its pneumonic and septicemic variations. Other diseases, such as dysentery and smallpox, may have occurred at the same time. Zoologist Graham Twigg, in his book The Black Death: A Biological Reappraisal (1985), assesses the spread of the disease, death rates, descriptions of victims, and ecological and climatic factors pertaining to the rat and flea populations that would have spread the disease in England. In his view, a more likely candidate is anthrax, a lethal bacterial disease that can be spread over a wide area via airborne spores, infecting and killing victims with chilling speed and producing symptoms that correspond to many historical accounts of the plague. It is just one theory; however, it represents the difficulty of conducting epidemiological research across a gulf of six centuries.
Modern epidemiologists, meanwhile, have their hands full. The search to understand the origins and transmission of diseases continues. In 1999, for example, scientists traced HIV to a subspecies of chimpanzee in equatorial Africa. Other emerging diseases also demand attention—the Ebola virus is one notorious example. Scientists are watchful for a mutation of influenza virus that might produce another Spanish Flu, the name given to the great influenza outbreak of 1918 in the United States. A deadly flu strain killed more than half a million Americans that year, and upwards of 20 million people worldwide. Still another threat is posed by once-conquered infectious illnesses appearing again among human populations. For example, the tubercle bacteria, which causes tuberculosis, has developed resistance to antibiotics. Diseases may never again rampage in a climate of blind fear and medical ignorance as in the days of the Black Death, but the battle of humans versus pathogens goes on. Clearly, the science of epidemiology demands constant research and constant vigilance.
About the author: Christopher King is the editor of ScienceWatch, a newsletter that tracks the trends and performance in basic research, published by the Institute for Scientific Information in Philadelphia, Pennsylvania.
Appears in
Bacterial Diseases; Contagious Diseases; Plague; Dance of Death; Epidemic; Black Death; Human Disease
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