As we look back at millennia of misinterpretations, it becomes clear that science has a history of getting things wrong the first time around —and a lot of that has to do with the role of existing beliefs and prejudices.
So it’s not surprising that in past centuries, doctors misunderstood many deadly diseases that they used to treat in some truly horrifying ways.
Here are five devastating diseases that medical experts got entirely wrong the first time:

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#5 Epilepsy
Like cancer, seizure disorders have existed throughout all of human history. Seizures in general can happen to anyone, and for a multitude of reasons.
Those with epilepsy, however, may have seizures frequently – and can experience several different types. The best known, due to their highly visible nature, are grand mal seizures. These seizures involve not just a change in consciousness, but tonic-clonic jerking movements of the limbs and head.
Sadly, because of religious the beliefs of the times, both legitimate and illegitimate medical “experts” conflated epilepsy with demonic possession. These early religious beliefs held that demons had possessed the afflicted, and that God was punishing the individual for it.
The fear of demonic possession and God’s punishment ingrained itself so deep into ancient societies that they had epileptics isolated, shunned, and subject to what we today would consider to be grisly treatment. Those early “treatments” devised by the Romans involved the patient drinking the blood of fallen gladiators and eating the flesh of corpses, with these ceremonies influencing later exorcisms.

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#4 Syphilis
This disease was called by the ancient world a “pestilence,” and a plague as it moved quickly, overwhelming populations with fatality and disfiguration. Confounded medical professionals couldn’t seem to explain the disease away.
But the late 1400s, it became obvious that it was sexually transmitted. And soon enough, medical experts decided to blame women for the disease — specifically prostitutes.
While existing medical science indeed had a handle on the mode of transmission, social and institutional sexism continued to dictate that women stood at the source of all venereal diseases. So throughout the mid-19th century, doctors regularly infected prostitutes with syphilis in the hopes that they would develop immunity to the disease. Not surprisingly, the experiment didn’t work.
It was until the emergence of antibiotics that syphilis was finally treated with success.

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#3 Cancer
The various cancers that affect the human body have perplexed medical experts for centuries —especially those that prove fatal despite aggressive medical intervention.
This perplexity goes all the way back to ancient Greece, where religious sects prohibited any study of the human body after death. This, along with an obvious lack of instruments such as the microscope, left those interested in medicine with very limited knowledge of what the inside of the human body actually looked like.
With the practice of real medical science not being an option, ancient Greek physicians suggested that cancer came from bad fluids in the body. Some of the treatments included forcing those fluids with extensive ingestion of laxative remedies.
Because these early medical professionals couldn’t see what was happening at a microscopic level, they reported only what seemed immediately apparent to the naked eye. And in fact, the signs and symptoms of cancer — caused by unusual and harmful cellular proliferation — rightly led them to believe that something, somewhere, was growing out of control.
But it wasn’t until the 19th century, with the advent of the modern microscope that doctors developed a more robust understanding of how cancer works and began to devise treatments to slow its progress.
#2 Tuberculosis
For the earlier part of the 19th century and before, experts called the disease “consumption” caused by population growth. They claimed that the disease came largely due to “sorrowful passions,” a saddened mental and emotional state they attributed to the rapid changes taking place in the world at the time.
In the Middle Ages, the illness was known in England and France as “king’s evil”, and it was widely believed that persons affected could heal after a royal touch.
In the 12th century, William of Malmesbury reported complementary treatments including visits at royal tombs, the kings’ touch. The practice of the king’s touch established by English and French kings continued for several years. Queen Anne was the last English monarch to use this practice (1712).
In the Middle Ages, moreover, the French surgeon Guy de Chauliac proposed the surgical removal of the scrofulous gland as a cure for the disease.
The advent of penicillin practically eradicated it in the following century.

#1 Leprosy
Leprosy is perhaps one of the most tragically misunderstood diseases in history. Like many diseases before it, ancient medical professionals originally believed it was either something inherited or a form of punishment made manifest with disfigurement.
In either case, leper patients were shunned, quarantined and sent to “leper colonies ” where they would live out the remainder of their lives in isolation.
Because people feared catching leprosy so much, some European villages even rang bells to alert residents that a person with leprosy was nearby, so that they could avoid walking in the afflicted’s direction.
Unlike some diseases at first believed to be God’s punishment, the stigma surrounding leprosy remained even after researchers discovered its biological cause. Sufferers were shipped off to sanitarium hospitals or entire colonies for treatment, and many of them would live out the rest of their lives away from the rest of society.
Isolation continued even as understanding about the disease and its treatment became commonplace: Sufferers were shipped off to sanitarium hospitals or entire colonies for treatment, and many of them would live out the rest of their lives away from the rest of society.
In an effort to de-stigmatize the condition, physicians nowadays refer to it as Hansen’s Disease. They also note that as much as 95 percent of the population may be naturally immune to leprosy, and if one does contract it, it’s most likely to come from an armadillo, not a fellow human.
As we look back and can’t imagine how our ancestors could have been so wrong on these diseases, we must remember that future generations may look back at us and wonder why we couldn’t see the answers to medicine’s biggest mysteries — which might be right in front of us.