By the spring of 1348, the city of Avignon, where the Pope then lived, had become a charnel house. Eleven thousand people were carried into a single new cemetery between the middle of March and the end of April. The man who recorded that number was a musician named Louis Heyligen, a Fleming in the household of Cardinal Giovanni Colonna, a long way from home. On the 27th of April he sat down and wrote to friends in Bruges, telling them what he was watching.

Half the city was dead, he said. The Pope had bought a field for the overflow, and it had filled within six weeks. The doctors had told him the sickness took three forms, and he set them out one by one: the one in the lungs that killed within two days and spared nobody, the one with swellings under the arms and in the groin, and the one with fever and swellings together. The sick were fleeing the well, he wrote, and the well were fleeing the sick, and he did not know whether he would live to see the letter delivered.

He did. Most of the people he was describing did not. The plague reached the West in October of 1347, when twelve Genoese galleys put into the harbor at Messina in Sicily with sailors dying on board. Behind those ships lay the Black Sea and the trading post of Caffa, where a Tatar army besieging the Genoese walls was itself being destroyed by the disease.

In the accounts, the Tatars loaded their dead onto catapults and hurled the corpses over the walls, and the stench inside the crowded city became unbearable, and the Genoese who fled by sea carried the sickness home with them. From Messina it went everywhere: Genoa and Pisa by the turn of the year, Marseille by November, Avignon by January of 1348, Florence and Siena in the spring, Paris by the summer. It came ashore in England at Melcombe in Dorset around the end of June 1348, reached London by the autumn, and worked north through the whole of 1349. Norway is said to have gotten it from a ship that drifted into Bergen with everyone aboard already dead.

By 1352 it was in Moscow. The accepted figures put the dead somewhere between a third and three-fifths of Europe’s population in five years: twenty-five to fifty million people. The bacterium responsible has been identified with remarkable precision. In 2011, a team took teeth from skeletons in the East Smithfield burial ground, the emergency cemetery London opened in 1348 when the churchyards filled, and pulled Yersinia pestis DNA out of the dried pulp inside.

They rebuilt the whole genome. The organism that emptied medieval London differs from the modern strain by only about ninety-seven letters out of four and a half million. It is near enough the same organism that still kills a few hundred people a year today. The medieval doctors recognized three forms of the disease without knowing its cause.

The first and most common was bubonic. A flea, usually one that had fed on a dying rat, bit a person on the leg or ankle. Nothing happened for two days, sometimes as many as seven. Then came a fever that shot past thirty-nine degrees, a headache described as a blow, shivering fits, aching in the back and thighs, vomiting, sometimes with blood in it.

Within about a day, the bacteria reached the nearest lymph node, and the node began to swell. If the bite was on the leg, that meant the groin; if on the arm, the armpit. The node filled and swelled to the size of an egg, then an apple, and the skin over it stretched tight and turned red, then purple, then black. Black or livid blotches appeared on the arms and thighs, bleeding under the skin.

The English called them God’s tokens. The buboes were so tender that patients could not bear the weight of a sheet on them. Some stayed hard; some softened and burst, releasing a thick greenish-yellow pus with a smell people wrote about specifically. The infection spread into the blood.

Within two or three days, a patient who had been lucid and terrified became confused, then incoherent, then unconscious. From the first shiver to death was most commonly three to five days. Untreated bubonic plague killed somewhere between thirty and sixty percent of those who caught it. To the people in the streets, it felt like a lottery drawn in front of them twice a day.

The second form was pneumonic plague. When the bacteria reached the lungs, the incubation dropped to a day or two. The patient woke with a fever and a headache and a tightness in the chest, and began to cough. At first dry, then with thin watery sputum, then streaked, and by the second day, bright red frothy blood, mouthfuls of it.

The air sacs of the lungs were filling with blood and fluid, and every breath churned it. Untreated pneumonic plague is as close to universally fatal as any disease known. The dying felt suffocation, slow and then fast, their lips and fingernails going blue, drowning in their own beds while every cough sprayed the room. This is the form behind the medieval observation that people caught it merely by looking at one another, airborne transmission described four hundred years before anyone had a word for it.

The third form, septicemic, happened when the bacteria flooded the bloodstream directly. The body’s clotting system went haywire, so the victim bled and clotted simultaneously. Blood seeped under the skin in purple sheets, came out of the nose, the gums, the bowel, and the tissue died. Fingers went black, toes went black, the tip of the nose went black.

This form killed almost everybody it touched, sometimes within a day, before a bubo ever had time to rise. People spoke of victims going to bed healthy and being found dead in the morning. The dying were attended by physicians who could do nothing. Guy de Chauliac, the Pope’s own physician at Avignon, caught the disease himself and lived to write about it.

He admitted that the plague was most humiliating for the doctors, since they could do no good and dared not visit the sick for fear of infection, and when they did visit, they earned nothing since all who caught it died. He himself waited it out at Avignon out of what he called a determination to avoid infamy, and caught it, and recovered after six weeks. The cardinal Heyligen served died that summer. The Pope, Clement VI, on de Chauliac’s advice, shut himself in his chamber with a large fire burning on either side of him, and sat between the two fires through the Provençal summer, seeing almost no one.

The theory was that the flames purified the corrupt air. Whether or not the fires kept the fleas away, the Pope came through. Florence lost perhaps half its people. Giovanni Boccaccio, whose Decameron opens with the most famous description of the plague ever written, recorded that corpses were carried out of houses and left at the doors in the morning for the bearers to collect.

The churchyards filled, and the Florentines dug enormous trenches beside the churches, and bodies went into them by the hundred. A boy who lived through it, Marchionne di Coppo Stefani, later wrote that the bodies were laid in with a little earth between the layers, the way you put layers of cheese in a lasagna. The gravediggers got rich, charging what they liked. Boccaccio also told one small story: the rags of a poor man who had died of the plague were thrown into the street, and two pigs came along and rooted in them, and within the hour both pigs went into convulsions and dropped dead.

He offered it as proof of how the sickness clung to whatever the dead had touched. South of Florence, in Siena, the shoemaker Agnolo di Tura kept a record that is harder to read than Boccaccio’s. The mortality began in Siena in May of 1348. Fathers abandoned children, wives abandoned husbands, and nobody could be found to bury the dead for money or friendship.

People carried their own dead to the trenches without a priest, without an office, and tossed them in. The bells did not ring for anyone. The ditches were shallow, and dogs came at night and pulled corpses out and ate them in the streets. And in the middle of all that, one plain sentence: “And I, Agnolo di Tura, called the Fat, buried my five children with my own hands.

” The city’s great cathedral, which the Sienese had been enlarging into the biggest church in Christendom, had its workforce wiped out, and the project was abandoned. The unfinished walls are still standing. In England, the disease came ashore in Dorset around midsummer of 1348 and reached London in the autumn. The canon Henry Knighton described sheep and cattle wandering untended through the fields and crops rotting where they stood, with nobody left to bring them in.

Prices collapsed. A good horse worth forty shillings went for six and a half. When the survivors later started to want things again, no hands were left to make them, and wages doubled, which Knighton, a landowner’s man to his bones, found almost as scandalous as the deaths. He also recorded what happened to the Scots.

Hearing that the plague was destroying the English, they gathered an army in the forest of Selkirk in 1349 to take advantage of it and laughed at the English for their misfortune. Then the plague reached the camp. About five thousand died there in a short time, the survivors broke up and went home to their villages, and took it with them, so that the sickness became a Scottish one within the year. The church in England saw it coming.

In July of 1348, before the disease reached his province, the Archbishop of York ordered processions and prayers every Wednesday and Friday to turn it aside. In January of 1349, the king postponed Parliament on the stated grounds that the plague had grown so bad in Westminster that it would be too dangerous for the Lords and Commons to gather. Somewhere between a third and half of the benefited clergy of England died in the space of a year, a figure derived from bishops’ registers that recorded every vacancy. Priests died for the same reason physicians did: they went into the rooms.

And when they stopped going in, a problem arose that terrified medieval people far more than the physical pain: dying unshriven, without confession and absolution, facing judgment with your sins still on you. In January of 1349, the bishop of Bath and Wells instructed that anyone in danger of death should make their confession to any lay person to hand, and he added, to a woman if a man was not available. That was an astonishing thing for a bishop to write. Across the west of England that winter, dying men and women whispered their sins to a neighbor, a servant, a child, whoever was in the room and had not run.

The pit at East Smithfield is where all of this can still be seen. The city bought the land in 1348 when the parish graveyards were full. When it was excavated in the 1980s, archaeologists found long trenches with bodies laid in rows up to five deep, most in shrouds, some in coffins, children tucked in beside adults. They counted over 2,400 individuals.

What struck the excavators was how orderly it was. Somebody had kept the rows straight. Somebody had faced the bodies east. In the middle of the worst thing that had ever happened to the city, men were still standing in a trench doing the job properly.

The plague took two royal deaths. Princess Joan, daughter of Edward III, was traveling south in the summer of 1348 to marry Pedro, heir to Castile. She was fourteen. Her party landed at Bordeaux, and despite a warning that the sickness was in the city, they stayed.

Joan died on the 1st of July. Her father wrote to Alonso of Castile that he had lost a daughter in whom all the virtues had been gathered. Her intended father-in-law refused to lift the siege he was conducting at Gibraltar when the plague appeared in his camp, and it killed him on the 27th of March 1350. He was the only reigning king in Europe to die of it.

The plague did not leave after 1350. It came back in 1361 and in 1369 and in 1375 and in the 1390s, and it kept coming back somewhere in Europe every few years for three hundred years. A man born in 1400 could expect to see it come through his town four or five times in his life. The second wave in 1361 was called the pestis puerorum, the children’s plague, because anyone alive who had been an adult in 1349 had either died or come through with some resistance, while the children born since had nothing.

The disease that had taken the grandparents and the uncles in the first wave took the children in the second. What could a physician actually do? He could bleed you, opening a vein with a lancet and letting the blood run into a bowl until you fainted. He could open the bubo with a knife if it had softened, and cauterize the wound with a hot iron.

He could apply poultices of figs and onions cooked soft with yeast and butter, or stranger things. At the top of the market was theriac, a paste of anywhere from forty to seventy ingredients, including viper flesh, cinnamon, myrrh, and a serious quantity of opium, which took the edge off the pain and let you sleep. Some physicians took a living chicken, plucked the feathers from its backside, and pressed the bare skin onto the swelling, on the theory that the bird would pull the poison out of the patient and into its own body. The cure was working when the bird began to droop and finished when the bird died.

The man in the bed usually died anyway. The one piece of advice that actually worked was the oldest: flee quickly, go far, come back late. Most people could not flee, and the ones who could often carried it with them. Cities on the Adriatic learned this first.

In 1377, Ragusa ordered that anyone arriving from a plague area had to wait on an island for thirty days before entering. Venice later stretched that to forty, a quarantina, and the word quarantine grew out of it. It was the first real defensive measure anyone in Europe hit on, and it came from watching ships rather than from any theory of medicine. As the disease spread, a story spread ahead of it that the Jews were poisoning the wells.

The story seems to have started in the south of France in the spring of 1348, fed by confessions extracted under torture. In September of that year, a Jewish man called Agimet, under torture at the castle of Chillon on Lake Geneva, confessed that a rabbi in Chambery had given him a packet of poison to drop into the wells of Venice and other cities. Copies of that confession were sent around the Rhine towns as evidence. Strasbourg is the case best documented.

The plague had not yet reached the city, and the bishop and the town’s magistrates refused to act on the stories. So on the 9th of February 1349, the guilds rose, threw out the magistrates, and put in a new council. Five days later, on St. Valentine’s Day, the Jews of Strasbourg were rounded up, taken to their own cemetery where a wooden platform had been built, and burned alive on it.

Around two thousand died, by the account written within living memory of it. Those who agreed to be baptized were spared. The debts owed to the Jews were declared cancelled, and the money and pledges they had held were shared out among the guildsmen. The chronicler says in as many words that the money was the poison that killed the Jews.

Within the year the same thing happened in Basel, in Freiburg, in Mainz, in Cologne, in Erfurt, in Frankfurt. In some towns, the Jewish community set fire to their own houses and died inside rather than wait for the platform. Clement VI issued two bulls that year ordering the clergy to protect the Jews, pointing out that Jews were dying of the plague at the same rate as everyone else. Very few towns listened.

For the person in the bed, the culture around them was building an entire way of dying. The Ars Moriendi, the art of dying, set out what the dying man should expect. Five temptations came to the deathbed: doubt, despair, impatience, pride, and clinging to the things of the world, his money and his children. A good death, when it could be managed, went like this: the dying person propped up facing east, the priest coming with the host and a boy with a bell, confession whispered with everyone else sent out, anointing oil on the eyes and ears and nostrils and lips and hands and feet, the last communion, a blessed candle put into the dying hand, a crucifix held up before the eyes.

That was the death everyone hoped for and paid for and prepared for. Almost nobody got it in the summer of 1348, and the people who did not get it knew exactly what they were being denied. The plague gives the modern reader a clear picture of what it felt like, hour by hour, for the person lying in the bed. But it was only one door out of a house with many doors.

Leprosy ran on the opposite clock. The plague gave you five days; leprosy gave you twenty years, and spent them taking you apart a piece at a time while everyone you knew watched. It started at the surface, in the skin and the nerves just under it, at the cool places: fingers, toes, the tip of the nose, the ears. A patch of skin lost its color and its feeling.

The nerves running to the hands and feet thickened and died, the muscles wasted, and the fingers curled inward into a claw that would not open. Loss of feeling is one of the worst things that can happen to a body. A man with dead nerves in his hands picked up a pot from the fire and did not feel it burn. He walked on a foot with a stone in the shoe until the sole was an open ulcer.

He slept while a rat gnawed his fingertip and woke with a wound he could not explain. Over years, the fingers and toes shortened and came off. Meanwhile the face was changing. In the severe form, the skin thickened into nodules, the brows fell out, the nose collapsed into the face, the voice went hoarse, and the eyes went blind.

Diagnosis was a formal event, and the stakes were enormous. If the panel said yes, the law took over. The Lombard King Rothari had ruled in 643 that a leper expelled from the community was to be treated as if dead. By the later Middle Ages, there was a liturgy for it.

The leper was brought to church wearing a black cloth and mass was said as if he were dead, with him kneeling under a black pall where a coffin would go. Then the priest walked him to the churchyard, to an open grave, and threw three spadefuls of earth over his head and said the words: be dead to the world, alive again to God. Then came the restrictions. He was forbidden to enter a church, a mill, a bakehouse, a market, or a tavern, to wash in a spring or stream, to touch anything he wished to buy except with a stick, to touch children, to walk barefoot, to speak to anyone downwind, to eat with anyone but lepers.

He was given a clapper or a bell to sound as he came, so people could clear the road ahead of him. Where he went afterward depended on money and luck. Across Europe stood the leper hospitals, and in a well-run one, he would rise for prayers, eat bread and pottage, have his ulcers washed and dressed, and be buried in the hospital’s own ground when the time came. Ergotism came out of the bread.

In wet years, a fungus infected rye and replaced individual grains with hard purple-black growths that carried alkaloids which clamped down the blood vessels, and in a different dose acted on the brain. A village that had a wet summer and ate its own bread all winter could poison itself in slow motion without ever knowing why. The gangrenous form was called the holy fire. It began with a burning sensation in the hands and feet, then the limb went cold, then pale, then blue, then black, and the flesh dried and hardened and shrank onto the bone.

Accounts describe people whose feet fell off while they were walking. The convulsive form brought violent muscle spasms and vivid hallucinations of demons and animals and fire. Around 1095, a nobleman whose son recovered at the shrine of St. Anthony founded a hospital order that specialized in exactly this disease.

The hospitals were recognizable by what hung over the door: amputated blackened limbs left by the cured as offerings. Inside, the patients were washed, given a balm made from pork fat and herbs, and fed on the hospital’s own bread made from clean grain. So they got better, and the brothers got credit for a miracle, even if they had not worked out why. The disease that came from nowhere, killed like nothing else, and left was the English sweating sickness.

It arrived in 1485, in the same season Henry Tudor landed to take the crown from Richard III. It killed within a day. It came again in 1508, in 1517, in 1528, and in 1551, and after that it never came again, five visits in sixty-six years, mostly confined to England. The onset was sudden and total.

A feeling of dread came before any physical sign. Then a cold shivering that shook the whole body, then pain in the head and neck and limbs, then within an hour or two, the heat and the sweat, pouring off the body, the bedding drenched, the sweat itself foul-smelling. There was an overpowering urge to sleep, and the physicians believed, as did most, that if you let them sleep, they died. So relatives were told to keep the patient awake by any means for a full day and night, talking to them, shaking them, slapping them if it came to that.

Within a day, it was over, one way or the other. The chronicler’s phrase everyone quotes: people married at dinner were dead at supper. What most disturbed contemporaries was who the sweat chose. Plague went for the poor and the crowded.

The sweat went for the healthy, the young, the well-fed, and it went for men more than women. In 1528 it got into Henry VIII’s household, and the king, terrified of illness, fled from house to house for weeks, changing lodgings whenever a case appeared near him. Anne Boleyn caught it and lived. Her brother-in-law caught it and died within hours.

Nobody knows what the sweating sickness was. It simply stopped. Childbirth killed women at every rank. A great many pregnant women made their wills before their time came.

The chamber was closed, windows shuttered, fire lit, men excluded, the midwife and neighbor women in attendance. If the birth went well, most did, and the birth girdle, a strip of parchment written over with prayers to St. Margaret, got the credit. If it did not go well, almost nothing could be done.

A child lying crossways could not be turned by anyone who did not know how, and few did. A head too large for the pelvis in a mother whose own bones had been bent by childhood rickets would not pass, and the labor went on for a day, then two, then three, until she died of exhaustion or the infection that followed. If the afterbirth did not come away, or the womb did not clamp down, she could bleed out onto the straw in minutes. And if she came through the birth, the danger was not over, because childbed fever was waiting.

Two or three days after delivery, a mother would begin to shiver, and the belly would swell, and within a week she would be dead of an infection carried into her body on the unwashed hands of the very women trying to help her. The famine came thirty years before the plague, and the frail bodies in the East Smithfield trench were made in it. The rain started across northern Europe in the spring of 1315, and it did not stop. It rained through the summer, the crops rotted in the fields, the hay could not be cut, and the animals had nothing for the winter.

The next year was as bad, and the year after not much better. Grain prices went up threefold and fourfold. People ate dogs, cats, horses, the bark of trees, grass, roots. In August of 1315, King Edward II stopped at St.

Albans, and his household could not find bread to buy for the king of England at any price. The chroniclers record parents abandoning their children, children sold, and in more than one place, people eating the dead or killing to eat. Starvation has a course. The body burns its fat first, then its muscle.

The belly swells with fluid while the limbs shrink to sticks. The gums bleed. Wounds do not heal. Children go first, having the least to burn.

Those who lived through it came out of it with bones that showed it for the rest of their lives. And thirty years later, those were the bodies that went into the plague pits, already frail before they got sick. The famine and the plague were one event with a gap in the middle. One last voice, from the plague years in Kilkenny, Ireland, in the summer of 1349.

A Franciscan friar named John Clyn was keeping the annals of his house, and he kept them through the pestilence. He wrote that in Kilkenny scarcely a house could be found in which only one had died, that the priest and the man he had confessed were often carried to the grave together, that many died of boils and abscesses and pustules on their shins and under their arms, and others frantic with pain in the head, and others spitting blood. He wrote that he had seen so much evil that he had put it all in writing while waiting among the dead for death to come, in case anyone of the race of Adam should survive it. And he asked any man who lived to carry on the work he had begun.

Then he left a stretch of blank parchment for them. After the blank, in a different hand, is one line: here, it seems, the author died.