Superstition trumped medical science during Medieval times. It wasn’t until the 1800s and the introduction of germ theory that people learned how disease was contracted and spread. Before the Age of Enlightenment, many people viewed sickness as punishment for sin. Diseases like mental illness and ergotism were seen as the devil’s handiwork. When the plague struck Europe, public officials realized it was a disease that should be quarantined, but beliefs of supernatural causation persisted within the population.

Personal Contact

Some diseases were believed to spread through human contact. For example, leprosy sufferers were required to wear long tunics, gloves and footwear to avoid infecting others, according to an article in "The Social Science Journal." People with leprosy were forbidden to speak unless they were downwind. Lepers were banned from bathing in rivers. Leprosy sufferers entering a public place were expected to announce their presence by ringing a bell because they were considered highly contagious.

Poisonous Vapors

Beginning in the Middle Ages, people believed that toxic vapors called miasma arose from the dirt and gave people diseases, such as malaria. At the time, scholars posited that a particular alignment of the planets had caused earth to release these toxic vapors. When an epidemic of measles struck London in 1670, scientist Sydenham attributed it to toxic miasma, which contradicted a theory proposed by physician Fracestero in 1546 that measles spread person-to-person.

Rotting Flesh

Decaying bodies were suspected of spreading plague known as the “Black Death,” which killed about one-third of Europe’s population in the 1300s. The bodies of plague victims were buried in mass graves or tossed into the Rhone River, causing an overpowering stench. Peasants believed that disease from dead bodies spread through the air, so they covered their mouth with handkerchiefs dipped in aromatic oil whenever they ventured outside. Herbs were burned in an attempt to filter the air, and magic spells were cast for added protection.

Infliction from Outsiders

Xenophobic attitudes in the Middle Ages led to prejudicial finger pointing. Jews were accused of spreading the plague by poisoning wells. Consequentially, Jews were brutally and unjustly persecuted. For instance, the population of Jews in Frankfurt dropped from 19,000 in 1350 to fewer than 10 by 1400, according to the JewishHistory.org website. Syphllis was another disease attributed to contact with outsiders. Sailors commonly attributed their veneral diseases to having sexual relations with a woman from another country. Russians called syphilis the “Polish disease.”