Ancient urbanites recognized some of these special hazards. Accounts going back 2,000 to 4,000 years tell of scourges carried by lice, bedbugs, and ticks—all disease-associated insects that the writers noted were more abundant in the dense housing conditions of the cities. Though their understanding of the relationship between these insects and specific diseases was muddy, writers in ancient Egypt, Greece, Rome, India, and China all drew attention to the insect problem. Similarly, Galen in Athens and Herodotus in Rome recognized a connection between the expansion of their cities into marshy areas and the increase in malaria.5 Chinese records dating back to 243 B.C. also noted massive epidemics—claiming millions of lives—which arose constantly from the cities of China’s far-flung empire.6
On the basis of historical accounts from Greece, Rome, Europe, and the post-Columbian Americas, twentieth-century scholars have tried to interpret which diseases plagued ancient urban centers. For example, during the Peloponnesian War of 430 B.C. a devastating epidemic hit Athens, probably imported by returning soldiers. Thucydides said of it, “No scourge so destructive of human life is anywhere on record. The physicians had to treat it without knowing its nature, and it was among them that the greatest mortality occurred.â€
It was later thought that the epidemic, which Thucydides said caused illness in every Athenian and killed up to half the population, was either typhus, the plague, or smallpox.7 Hundreds of great global pandemics followed. Four diseases that seemed to William McNeill and other medical historians of the 1970s to have gained particular benefit from the urban ecology over the previous 2,000 years were pneumonic plague, leprosy (Hansen’s disease), tuberculosis, and syphilis. As far as could be discerned from historical records, these were rarely—if ever—seen prior to the establishment of urban societies, and all four exploited to their advantage human conditions unique to cities.
The world has experienced at least two great pandemics of bubonic/ pneumonic plague, a disease caused by the Yersinia pestis bacterium—carried by fleas which resided on rodents, particularly rats. Though the bacterium has never been eradicated, ideal ecological conditions for its rapid spread among Homo sapiens occurred only a handful of times in recorded human history. Once Y. pestis got into the human bloodstream, either via a flea or rat bite or by inhalation of the bacterium, it quickly made its way into the lymphatic system. There, the bacterium killed massive numbers of cells, giving rise to formation of often grotesque pustules and pus-filled boils. Bacteria produced in these infected sites then migrated to the liver, spleen, and brain, causing hemorrhagic destruction of the organs and demented behavior that during the Middle Ages was interpreted as intervention by Satan.
The occasional case of plague was seen during the twentieth century,8 but well before humanity had invented antibiotics to treat it, the disease had ceased to threaten further pandemics.
Sometime around 1346 the Black Death began on the steppes of Mongolia: infected fleas infested millions of rodents which, in turn, raided human dwellings in search of food. Why the disease emerged that particular year was never clear, though scientists in the 1980s speculated that the weather may have favored a rodent population explosion. The disease made its way rapidly across Asia, carried by fleas that hid in the pelts of fur traders, the blankets and clothing of travelers, and the fur of rodents that stowed away aboard caravans and barges crisscrossing the continent. Rumors of the Asian scourge preceded its arrival in Europe, and it was said that India, China, and Asia Minor were literally covered with dead bodies.9 The Chinese population plummeted from 123 million in 1200 to 65 million in 1393, probably due to the plague and the famine that followed.
It reached the prosperous European trading port of Messina, Sicily, in the fall of 1347 aboard an Italian ship returning from the Crimea, and immediately exploited the city’s ecology. Rats from the plagued ship joined the abundant local rodent population. Ailing men from the ship passed the bacteria on to the Messina citizenry directly, exhaling lethal microbes with their dying gasps.
As the plague made its way across Europe and North Africa, each city anticipated its arrival and tried by a variety of means to protect itself. Travelers were barred entry, drawbridges were raised to seal the wealthy urbanites off from their less fortunate peasantry, great purges and outright slaughter of tens of thousands of Jews and alleged devil worshippers were staged. The city of Strasbourg alone savagely slew 16,000 of its Jewish residents, blaming them for spreading the Black Death.10
Some who had no scapegoats blamed the plague on their own lack of piety. The Brotherhood of Flagellants were Christian men who daily beat themselves to the edge of death to purge the sins that were responsible for their disease. All over Europe, these men, encouraged by crowds of crazed aristocrats and peasants alike, would thrash themselves with leather whips embedded with small iron spikes.
The terrorized European population did everything save what might have spared them: ridding their cities of rodents and fleas. The cities fell not only because of rat infestations but also due to both human population density and hygienic conditions. Bathing was thought to be dangerous, and few Europeans ever washed, making them fertile ground for flea and lice infestation.
The pneumonic form of the plague, which rarely spread in less populated rural areas, was easily transmitted inside the densely populated medieval cities. Once a rat-driven bubonic form took hold, pneumonic cases in humans soon appeared, spreading the disease with terrifying rapidity.
Each city would be in the grip of the disease for four or five months, until the susceptible rats and humans had died. The survivors would then face famine and economic collapse, caused by the sharp reduction in workforces.
The daily death rates were staggering: 400 in Avignon; 800 in Paris; for Pisa, 500; Vienna buried or burned 600 bodies per day; and Givry, France, 1,500 daily. By the end, London, with a pre-plague population of 60,000, had lost 35,000. Half of Hamburg’s and two-thirds of Bremen’s populations perished. Most historians believe that at least one-third of Europe’s total human population (20 to 30 million people) died of the plague between 1346 and 1350.11 The highest per capita losses were consistently in the cities.
Over subsequent centuries, there were numerous outbreaks of urban plague in Europe, Asia, and the Middle East, though few spread far beyond the cities due to quarantines and to slow improvements in hygienic conditions.
In 1665, London suffered the Great Plague, a Yersinia epidemic that claimed over 100,000 lives in a year’s time. The epidemic began a year earlier, probably in Turkey, and was carried by trading ships to Amsterdam and Rotterdam and on to London during the winter of 1664–65. By that summer as many as 3,000 of the city’s residents perished each day.
The royal family and the aristocracy fled at the first sign of pestilence, taking up residence in the English countryside. The residents of London, the world’s largest and most densely populated city, were left to fend for themselves. They lived in thatch-roofed, brick, and wood row houses: an ecology made in heaven for rats.
In considering the pestilence a generation later, Daniel Defoe recommended that city authorities in the future
… not let such a contagion as this, which is indeed chiefly dangerous to collected bodies of people, find a million of people in a body together, as was very near the case before … . The plague, like a great fire, if a few houses only are contiguous where it happens, can only burn a few houses; or if it begins in a single, or, as we call it, a lone house, can only burn that lone house where it begins. But if it begins in a close-built town or city and gets a head, there its fury increases: it rages over the whole place, and consumes all it can reach.
Shortly after the plague subsided, in 1666, London was overcome by a real fire that engulfed most of the city. McNeill believed it was the Great Fire which stopped the Great Plague, burning off the thatch roofs, which were replaced with tile and slate.
Leprosy, as it w
as then called, claimed only a fraction of the lives felled by the plague, but was no less feared. Throughout history leprosy was dreaded more for its disfiguring and crippling effects on the human body than for its slow capacity to kill.
By the 1970s leprosy would be referred to as Hansen’s disease (named after Armauer Hansen, who in 1873 described the first definitive differential diagnosis of the disease) by those who wished to separate the bacterial ailment from the centuries of horror and prejudice that went with the word “leper.â€
There was great debate in the latter half of the twentieth century about the age of the Mycobacterium leprae organism and how long it had been producing significant disease in human beings. Though the Bible referred to ancient Hebrews suffering disfiguring diseases often translated as leprosy, the usually meticulous records of Egyptian scribes bore no hint of it. Searching for evidence of bone damage produced by the gnawing bacteria, studies of skeletons revealed no sign anywhere in the world prior to A.D. 500, when apparently leprotic bones were buried in the graveyards of Cairo, Alexandria, and parts of England and France.
A previously unrecognized disease did, however, sweep over Europe.12 Leprosy seemed to follow the rise of European cities during the medieval period, reaching a peak sometime around 1200. Nobody was certain then, or now, exactly how the fussy, slow organism was passed from one person to another. It obviously required close contact, but may have originally been more easily transmitted among the then totally nonimmune Homo sapiens. Once in a person’s body, however, M. leprae attacked the nerves and skin cells of cooler, peripheral parts of the body, causing them to go numb, weaken, and often be destroyed as a result of unfelt injuries. The disfigurement that resulted from loss of fingers, toes, ears, noses, and other external body parts marked “lepers†as targets for stigmatization and fear.
By 1980 most of the world’s five billion humans had antibodies to M. leprae, proving they’d been exposed without apparent harm.
But in medieval Europe leprosy took a high toll and seemed to spread rapidly through the congested cities. Some biologists in the 1980s theorized that factors unique to medieval urban life helped promote the mycobacterium’s spread, including the lifetime avoidance of bathing, always wearing wool rather than cotton clothing, and the practice of sharing bedding to stay warm.
Whatever the case, European leprosy died out with the Black Death of 1346. Nobody was certain why this was so, but it was generally suspected that the Black Death decreased the human density of urban areas, thus reducing human-to-human contact. It may also have been possible that plague survivors’ immune systems were less susceptible to a broad range of bacteria, including both Yersinia and M. leprae. Or conversely, those who were vulnerable to leprosy may have also been less able to respond to a range of other bacterial assaults.
In leprosy’s place, exploiting the post-plague urban chaos, came tuberculosis. Unlike the leprosy bacterium, M. tuberculin was truly ancient, and clear evidence of its affliction of Homo sapiens dated back to at least 5000 B.C.13 The disease was described by all ancient literate cultures, except those of the Americas, and archaeological evidence of bone damage predated the written descriptions of “consumption,†“phthisis,†or “tuberculosis,†as it was variously labeled. But the true impact of the disease wasn’t felt until after the Black Death when, according to theories popular in the 1980s, the tuberculosis organism exploited human ecological niches vacated by M. leprae. An urban environment was not required for its transmission, but it was clearly advantageous.
The rise of European tuberculosis was not sudden. Like leprosy, the organism was fastidious and slow-growing, producing overt and highly contagious illness only after months, or years, of infection. While the fastgrowing plague bacteria could kill a human in a matter of hours, few Homo sapiens were felled by M. tuberculin without prior years of debilitating illness.
On the other hand, the bacteria could be spread by airborne transmission, assuring that humans sharing close quarters with an afflicted individual would be exposed. By the 1980s scientists knew that infection did not guarantee illness or death: about one out of ten infected individuals eventually developed the disease, and without twentieth-century treatments about half would die.14
But conditions in European cities of the fifteenth to the seventeenth century were ideal for transmission of M. tuberculin, especially during the winter, when the practice was to shut all windows and huddle around a heat source. The microscopic droplets exhaled by a tuberculosis victim would drift continuously about the home.
The household might take steps to avoid exposure to visible droplets of coughed or sneezed tubercular material, but these were actually harmless. To take hold in the human body the bacteria had to be carried inside droplets small enough to pass through the barriers of the upper respiratory tract. Such tiny droplets could remain suspended in the air, drifting on currents, for days, containing live, infectious tuberculosis germs.15
There was only one thing seventeenth-century Europeans could have done to decrease their exposure to household tuberculosis: open the windows. One good flushing of the air could have purged 63 percent of the suspended infectious particles exhaled each day by an ailing resident, and the sun’s ultraviolet light would kill those organisms it reached.16
Medieval Europeans had no such options during the winter, however, particularly in northern latitudes. For poorer city dwellers especially, it was inconceivable to open windows during the winter, as fuel of any kind was scarce and extremely expensive. Europe’s wood had been used to build her cities.
The rates of tuberculosis slowly but steadily increased. The hardest-hit cities were also the largest, London particularly. By the time London was devastated by the Great Plague and subsequent Great Fire, one out of every five of its citizens had active tuberculosis. And this time the plague had no purging effect on a mycobacterial epidemic: the rates of TB continued to climb long after the 1665 plague passed.
As European explorers and colonialists made their way to the Americas, they carried the deadly mycobacterium with them, adding to the disease burden of tuberculosis, which had already for centuries plagued the Amerindian population.17 By the time the United States was torn asunder by the Civil War, tuberculosis was firmly entrenched in its northern cities, particularly Boston and New York City.
Between 1830 and the eve of the Civil War, Americans’ life expectancy and death rates fell to the levels that existed in London. In 1830, with a population of 52,000 citizens, Boston’s crude annual death rate was 21 per 1,000—half that of London at the time. By 1850, Boston’s crude death rate nearly equaled London’s, hitting 38 per 1,000. Tuberculosis wasn’t the only responsible factor, but it was a major contributor. Cases of consumption, as it was called, increased every year in Massachusetts, rising 40 percent between 1834 and 1853.18
The old families of New York City, Philadelphia, and Boston groaned in disbelief as their cities’ populations swelled, filth abounded, and disease ran rampant. Immigration, the Industrial Revolution, crowded slums, no public water supply, moral decay, no sewage systems—these were but a few of the factors that the civic leaders blamed for their crises.
The Western world’s urban crises peaked between 1830 and 1896, when Europe and North America suffered four devastating pandemics of cholera that spread primarily via the cities’ fetid water and sewage “systems.†Though physicians of the day didn’t understand why, quarantines didn’t work for cholera, so the rich generally fled the cities at the first hint of the dreaded dysenteric disease, leaving the common folk to fend for themselves. It would be decades before scientists could prove that cholera was caused by a bacterium that entered human bodies via contaminated food and water, and got into the water through the fecal waste of infected people.
The death toll from cholera in the nineteenth century due to waves of the disease was
astonishing: 10 percent of the population of St. Louis in three months during the 1849 epidemic;19 500,000 New York City residents in 1832; 8,605 Hamburg, Germany, residents in three summer months in 1892; 15,000 residents and hajj pilgrims in the city of Mecca, and some 53,000 Londoners, in 1847. The Mecca tragedy was repeated during the hajj of 1865, when 30,000 pilgrims to the city perished.
Though they had no idea what caused cholera, New York City authorities were appalled by the 1832 epidemic and blamed it on municipal filth. Reform followed. The Croton Aqueduct brought in clean drinking water for the first time, muddy streets were cobblestoned, and the squalid slums were slowly upgraded. As a result, subsequent waves of cholera took a minor toll.
Such was not the case in most other cities, however, where the connection between urban filth and disease remained a matter of vociferous debate among civic leaders. The fact that, without exception, cholera and other epidemic diseases—including tuberculosis—took their greatest toll among the most impoverished residents of the world’s metropolises seemed only to reinforce the belief by those in power from Moscow to Madrid that lower-class “immorality†was the root of disease.
During London’s devastating 1849 cholera epidemic, physician John Snow demonstrated that cholera was transmitted via water by removing the handle of the Broad Street pump, the sole water source for an impoverished and cholera-ridden community. The local epidemic, of course, came to a halt.
Authorities were unconvinced, however, so during London’s 1854 epidemic Snow mapped cholera cases and traced their water supplies. He showed that those neighborhoods with little cholera were receiving water drawn from the upper Thames, while cholera-plagued areas drew their water from the lower Thames, which included human waste from upstream.
Snow failed to convince authorities directly of the need to clean up water supplies, but the epidemics of cholera and other devastating diseases spurred improvements in basic urban hygiene all over the industrializing world. Citizens’ sanitary action groups cropped up in many cities, garbage and waste-disposal practices improved dramatically, outhouses were replaced by in-house toilet systems, and “cleanliness†became “next to godliness.â€
The Coming Plague Page 37