If you were a pilgrim or other traveller during the Middle Ages, you would have faced a whole host of dangers on the road, from bandits and pirates to harsh weather to wolves in the forest. But the encounter you would have feared most was with ghostly figures standing at the side of the road, dressed in rags and shaking rattles or bells to warn of their approach. Covered in sores and missing fingers and toes, they would beg you for alms, which you might give them before hastily rushing off, covering your mouth and nose with your cloak lest you contract their horrible affliction. These wretched figures were the lepers, sufferers of the dreaded disease of leprosy. Occupying the lowest rung of the Medieval caste system, lepers were declared legally dead by the church and banished to the margins of society, forbidden to interact with the non-infected and forced to beg by the roadside. Such was the stigma associated with this disease that to this day, the term “leper” remains synonymous with social ostracism. But just what is leprosy, anyway? Is it really as contagious as Medieval people believed? Does it really make your fingers and toes drop off? And is it still around today? Let’s find out as we dive into the fascinating history of one of humanity’s most feared – and misunderstood – diseases.

Just when leprosy first began to afflict humans is unknown. The term leprosy, from the Greek lepra or “scale,” has been around since at least Biblical times, with Leviticus 13:9-33 describing the disease as:

“Sometimes a skin disease will spread all over a person’s body, covering the skin from head to foot. The priest must look at that person’s whole body. If the priest sees that the skin disease covers the whole body and that it has turned all the skin white, the priest must announce that the person is clean. But if the skin is raw, that person is not clean. When the priest sees the raw skin, he must announce that the person is unclean. The raw skin is not clean. It is leprosy.”

However, it is generally recognized by scholars that the biblical affliction Tzaraath, often translated into English as “leprosy” refers not to the physical disease leprosy as we know it today but rather a spiritual condition brought about by ritual impurity, which could disfigure not only the human body but also clothing and walls or other surfaces in the home. And even if the term does refer to an actual disease, it is unclear whether this is actual leprosy or one of many other common skin diseases like eczema, psoriasis, vitiligo, or scleroderma. Similar descriptions in Ancient Egyptian and Ancient Indian texts are equally ambiguous.

Whatever the case, the oldest confirmed case of actual leprosy dates from the 2nd millennium B.C.E., discovered in a skeleton unearthed in Balathal, Rajasthan, in 2009. The oldest case in the West was found in a skeleton unearthed that same year in Jerusalem, dating from the 1st Century C.E. Based on this and other DNA evidence, epidemiologists believe leprosy spread from the Indian subcontinent to Eurasia around the 4th Century B.C.E., possibly carried by the armies of Alexander the Great. By the 12th Century C.E., the disease was well-established – and widely feared in Europe – so much so that during the Third Lateran Council of 1179, the Catholic Church declared that sufferers must be banished – not only from regular society, from the realm of the living. Upon receiving a diagnosis, lepers were subjected to a bizarre ritual known as the “lepers’ mass”, wherein they were made to kneel in an open grave while a priest poured cemetery earth over their heads three times, symbolizing that they were now “Dead unto the world but alive unto Christ.” The priest then read off a long list of prohibitions, condemning the leper to a life of ostracism and isolation:

“I forbid you to enter the church or monastery, fair, mill, market-place, or company of persons…ever to leave your house without your leper’s costume…to wash your hands or anything about you in the stream or fountain. I forbid you to enter a tavern…I forbid you, if you go on the road and you meet some person who speaks to you, to fail to put yourself downwind before you answer…I forbid you to go into a narrow lane so that if you should meet anyone he might catch the affliction from you…I forbid you ever to touch children or give them anything. I forbid you to eat or drink from any dishes but your own. I forbid you to eat or drink in company, unless with lepers.”

Lepers were also required to carry a bell or rattle to warn others of their arrival, could not be buried alongside the uninfected, and were limited to living in special hospitals or colonies called leprosaria. These were located well outside towns and cities, but always along a main road, for the only means available to lepers for earning a living was begging for alms to passers-by. But even this marginal existence was arguably better than the alternative, for in many places lepers were burned alive to prevent the disease from spreading. And while lepers could only lodge in leprosaria, there was no law confining them to the grounds, meaning they could roam at will so long as they followed the many rules previously outlined.

Strangely, while lepers were most often subjects of fear, they simultaneously occupied a unique position in Medieval spiritual life. Neither truly living nor yet dead, lepers were seen as serving out their time in purgatory here on earth. Thus, giving alms to lepers – often in exchange for their blessings – was believed to reduce one’s own time in purgatory and was encouraged by the church. The association between Jesus and lepers – whom he healed in one of his many miracles – granted them further spiritual significance. They were, in a strange way, considered uniquely blessed by God.

Examining the common symptoms of leprosy, it is easy to see why it has inspired such fear and revulsion. The first symptom of the disease is typically the appearance of stiff, dry, discoloured patches of skin all over the body, followed by the formation of thick skin nodules and ulcers which can cause horrible disfigurement. This is followed by muscle weakness, hair loss, and loss of sensation in the extremities – the latter of which results in the most famous symptom of leprosy: loss of fingers and toes. However, these digits do not actually “drop off” as is commonly believed. Rather, loss of sensation makes leprosy sufferers more likely to accidentally injure themselves, leading to tissue loss and secondary infections that cause the body to reabsorb damaged cartilage – and the digits along with it. This phenomenon is also responsible for one of the other classic signs of leprosy: a collapsed or “saddle” nose caused by the reabsorption of nasal cartilage. If the nerve damage spreads to the eyelids, sufferers can become insensitive to dust and other foreign objects, resulting in corneal scratching and ulcers and eventually blindness. Meanwhile, leprosy can also slowly suffocate its victims as the nodules and ulcers block their nasal and throat passages – lovely.

In addition to being horrifying, leprosy was extremely common during the Middle Ages – an unusual fact, for reasons we will get to shortly. From 1100 onwards the disease spread like wildfire across Europe, such that by 1300 there were some 19,000 leprosaria across the continent. At its height, leprosy is thought to have infected up to 1% of the European population. But then, around 1400, cases of the disease fell precipitously – for reasons that are not yet fully understood. One theory is that extreme quarantine measures imposed by the Church actually worked, causing transmission rates to plummet and natural immunity to the disease to spread through the population. Another theory credits the spread of tuberculosis across Europe during this period. Indeed, the causative agents of both diseases are very similar, and infection with one is thought to confer immunity to the other. But the most common – and darkest – explanation has to do with an even more famous disease that swept through Europe in the mid-14th century: the Bubonic Plague or Black Death. Leprosy sufferers, with their already weakened immune systems, would have been particularly vulnerable, causing most of them to be wiped out.

For much of history, Leprosy was thought to be either inflicted by God, caused by miasma or “bad air,” or a congenital condition passed down through families. In 1873, however, Norwegian physician Gerhard Armauer Hansen discovered that the disease was actually caused by the microorganism Mycobacterium leprae. It was the first time in history a bacterium was definitively linked with human disease. In honour of this discovery – and to combat the stigma associated with the disease – today leprosy is most often referred to as Hansen’s Disease.

Yet despite such breakthroughs, the stigmatization and banishment of leprosy sufferers remained commonplace. Perhaps the most famous contemporary example of this practice took place in Hawaii, where leprosy first arrived in 1866. That same year, the Hawaiian legislature passed a law declaring that lepers would be declared legally dead and banished to a remote colony on the island of Moloka’i. While the colony was meant to be self-sustaining, the residents’ advanced illnesses often prevented them from farming productively, leaving them on the brink of starvation. In 1874, Bishop Louis Maigret of the the Catholic Archdiocese of Honolulu asked for volunteers to help improve conditions on Moloka’i. Four priests volunteered, and one was selected: Belgian-born Joseph de Veuster, better known as Father Damien.

On arriving at the Moloka’i colony, Father Damien was shocked at the squalid living conditions, which he described in an 1886 report to the Board of Health:

“The smell of their filth, mixed with the exhalation of their sores, was simply disgusting and unbearable to a newcomer. Many a time in fulfilling my priestly duties at their domiciles, I have been compelled not only to close my nostrils, but to run outside and breathe the fresh air…At that time the progress of the disease was fearful, and age rate of mortality very high. In previous years, having nothing but small, damp huts, nearly the whole of the lepers were prostrated on their beds, covered with scabs and ugly sores, and had the appearance of very weak, broken-down constitutions.”

Despite these challenging conditions, Father Damien remained at the colony for the next 15 years, working with native Hawaiian superintendent William P. Ragsdale to improve living conditions by building and maintaining homes, hospitals, orphanages, churches, schools, and other amenities. Throughout his tenure, Damien ignored common wisdom regarding the transmission of leprosy, freely sharing food and his pipe with the colony residents in order to gain their trust. Alas, it was to prove his undoing, for one day in 1884 he accidentally put his foot in scalding water and realized he felt nothing. He had contracted leprosy. Undeterred, Damien continued to serve the Moloka’i colony, his condition gradually worsening until, on April 15, 1889, he finally succumbed to the disease at the age of 59. It was an eerily fitting end, for in 1874 Bishop Maigret had introduced him to the colony with the words:

“Here is Father Damien, who wishes to sacrifice himself for the salvation of your souls.”

Following his death, Father Damien’s legacy was savagely attacked by Presbyterian minister Reverend Charles McEwen Hyde, who blamed Damien’s death on his own carelessness and accused him of taking credit for measures originated by the Hawaiian Board of Health. To Damien’s defence came no less a figure than Scottish author Robert Louis Stevenson, who travelled to Hawaii in 1886 seeking a cure for his tuberculosis and interviewed several residents of the Moloka’i colony. In a written rebuttal to Reverend Hyde, Stevenson concluded that:

“[Their testimonies] build up the image of a man, with all his weakness, essentially heroic, and alive with rugged honesty, generosity, and mirth.”

100 years later, Father Damien’s service and sacrifice were recognized when, in 1995, he was beatified by Pope John Paul II. In 2009, he was canonized by Pope Benedict XVI as Saint Damien of Moloka’i, patron saint of – who else – lepers.

Incredibly, the Moloka’i leper colony did not close until 1969, having been home to nearly 8,000 people over its 103 year history. The only leprosarium in the mainland United States lasted even longer. Located in Carville, Louisiana, the facility was established in 1894 on the site of an abandoned sugar plantation and operated by the Daughters of Charity of St. Vincent de Paul until 1905, when the hospital was taken over by the state of Louisiana. In 1921, administration transferred to the US Public Health Service, who renamed the facility the National Leprosarium. As in earlier periods of history, life for the patients was extremely restricted. They were not allowed to vote, marry, or live with their spouses if they were not also patients. However, things began to change in the 1930s when a patient named Stanely Stein founded a magazine called The Star, which he used to advocate for the improved treatment of leprosy sufferers. Stein soon found a supporter in Hollywood actress Tallulah Bankhead, who convinced many of her friends to buy subscriptions to The Star and even sent Stein a cast of her face when leprosy eventually blinded him. Thanks to Stein and Bankhead’s tireless advocacy, many of the draconian restrictions at Carville were lifted and the medical community began to adopt the term “Hansen’s Disease” over “leprosy.” Still the Carville Leprosarium persisted, until in 1999 the State of Louisiana gave the few remaining patients the option to leave in exchange for a $46,000 annual stipend. Some still chose to stay, with the last residents only leaving Carville in 2015.

Sadly, however, leprosaria are still not a thing of the past, with the practice of stigmatizing and ostracizing leprosy sufferers persisting in China, Thailand, and several African countries, and India, where there are still more than a thousand leper colonies still in existence. What makes this all the more tragic is that of all major human diseases, leprosy is now known to be the least transmissible, with 95% of the human population being naturally immune. And even if someone is susceptible, it takes prolonged, close contact with a sufferer – more specifically, infected droplets in their breath – to become infected, which is why it took 11 years living on Moloka’i for Father Damien to catch the disease. And once someone is infected, it can take up to 20 years for symptoms to appear. This makes the rapid spread of the disease during the Middle Ages particularly mysterious.

Also making the continued stigmatization of leprosy especially tragic is the fact that the disease is now treatable and even curable. But this was not always the case, with traditional remedies for leprosy including drinking the blood of various animals, administering the venom of scorpions and snakes, and elaborate spiritual purification rituals as detailed in Leviticus. Later, due to the similarity of its skin lesions, doctors attempted to treat leprosy in the same manner as syphilis: using highly toxic mercury. For most of human history, the only truly effective treatment for leprosy was Chaulmoogra Oil, derived from Hydnocarpus wightianus tree native to India. Unfortunately, the oil caused severe nausea when administered orally and painful abscesses when injected, meaning it was typically administered topically – the least effective delivery method. But in 1915 Alice Ball, the first black woman to obtain a Master’s in Chemistry from the University of Hawaii, discovered how to create an ethyl ester of Chaulmoogra Oil that was water-soluble, allowing it to be safely delivered via intramuscular injection. This discovery revolutionized the treatment of leprosy in Hawaii and around the world, and so impressed Ball’s professors that she was invited to teach chemistry at the University – the first black woman to do so. Tragically, Alice Ball would not live to see the fruits of her accomplishments. In March 1916, while giving a demonstration on the proper use of a gas mask, Ball accidentally inhaled a lungful of chlorine gas. She was sent to the mainland for treatment and returned in the fall to resume teaching, but the damage was too severe and she died on December 31, 1916 at the age of only 24. Credit for her discoveries was stolen by fellow chemist Arthur L. Dean, who named the the ester of Chaulmoogra Oil after himself and began mass-producing it. It was not until recently that Alice Ball’s contributions were finally recognized and her leprosy treatment renamed the “Ball Method.”

The Ball Method remained the standard treatment for leprosy until the 1940s, when it was replaced by the antibiotic diaminodiphenyl sulfone, better known as Dapsone. But while far more effective than Chaulmoogra Oil, Dapsone could not fully eliminate leprosy from a patient’s system, and thus had to be taken for life in order to keep the infection at bay. Worse still, by the 1960s the M. Leprae bacterium had begun developing resistance to Dapsone. As a result, the drug was combined with two other antibiotics – rifampicin and clofazimine – to create a potent multi-drug treatment or “cocktail” that can completely cure leprosy in six months and remains the standard treatment to this day. Also sometimes used is a drug with an infamous past: Thalidomide. Introduced in 1957, Thalidomide was originally sold over-the-counter to pregnant women as a treatment for morning sickness, but was eventually found to cause severe birth defects, causing it to be be pulled from shelves. However, in 1964, Israeli physician Jacob Sheskin administered thalidomide to a patient with severe leprosy and noted a significant effect on skin lesions. Due to its immune-modulating properties, thalidomide is also used in the treatment of cancers such as multiple myeloma and graft-vs.-host disease.

In the early 1980s, the World Health Organization launched a campaign to eradicate leprosy worldwide. By the year 2000, it succeeded in eliminating the disease as a public health concern – defined as less than 1 case per 10,000 people. However, leprosy still persists in certain regions, and is currently classified as a Neglected Tropical Disease by the WHO. Indeed, around 250,000 people contract the disease every year, with around half of those living in India. And in many places, even those who are cured still face stigma and ostracism due to the permanent disfigurement and nerve damage wrought by the disease.

While leprosy is largely a human disease, it has been found in other animals, including – strangely – nine-banded armadillos, whose body temperature of 32 degrees Celsius is ideal for the growth of M. Leprae. As leprosy did not exist in the Americas until the arrival of Europeans, the armadillos must have caught it from humans – a reversal of the typical transmission path for zoonotic diseases. Thankfully, however, the incubation period for leprosy is typically longer than the armadillos’ lifespan, meaning they rarely suffer from the effects of the disease. Leprosy has also been found in nonhuman primates such as chimpanzees and the cynomolgus macaque, and in European red squirrels. Indeed, DNA evidence from a pre-Norman Anglo-Saxon skull excavated in Hoxne, Suffolk in 2017 suggests that leprosy may have been transmitted to the British Isles via the trade in squirrel pelts and meat between the Saxons and the Vikings.

And this most misunderstood of diseases continues to offer up new surprises – including the unique ability to alter its hosts’ tissues to suit its own needs. In 2013, a team of biologists from the University of Edinburgh discovered that M. Leprae can genetically reprogram the cells of Armadillos to turn them back into undifferentiated stem cells. These can then be turned into whatever cells the bacterium needs to grow. For example, in one case M. Leprae grew its host’s liver to twice its normal size without it becoming cancerous or otherwise defective. The implications of this discovery are enormous, and could potentially lead to a whole new era of gene therapies to repair damaged organs. It seems the Medieval priests were right after all: leprosy is a strange sort of blessing.

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