Throughout millennia, people have fostered some pretty irrational ideas about how infectious diseases such as plague and cholera were spread. Some of those notions—like the idea that the ancient Cyprian plague could be caught simply by staring into the face of someone afflicted—seem laughable, like something the Monty Python troupe might have sprinkled into one of their medieval parody scripts for television.

Yet even as waves of disease washed again and again over population centers, it took centuries for science to fully understand the invisible world of microbes. Until that happened, people under pandemic siege tried to explain the overwhelming amount of death they saw in different ways. Some used simple observations, while some turned to fervent beliefs. Others viewed the cataclysm through the lens of their long-held biases, while still others processed the carnage through superstitions and bizarre theories. Here are a few:

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When masses of people started inexplicably dying, many early cultures looked first to a vengeful or unforgiving God—or gods. In ancient Greek mythology, which often served as allegory for actual events, Homer wrote in The Iliad of the god Apollo raining plague down on the Greek army with his arrows during the Trojan War, killing animals first, then soldiers. Apollo’s arrows came to symbolize disease and death.

For its part, the Bible carries numerous references to plague as the wrath of divinity:

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Throughout the centuries, plague arrived in wave after devastating wave, taking numerous forms—from bubonic (which affects the lymphatic system) to pneumonic (which attacks the lungs) to septicemic (which infiltrates the bloodstream). Perhaps the most virulent occurrence came in the mid 1300s with the Black Death, which felled more than 20 million people across Europe alone. While it’s largely believed that bacteria-carrying fleas were the main culprit, “experts” at the time found other explanations—especially in astrology and broadly formed ideas of “noxious vapors” as a breeding ground for pestilence.

In 1348, for example, King Philip VI of France asked the greatest medical minds at the University of Paris to report back to him on the causes of the bubonic plague. In a detailed document submitted to the crown, they blamed “the configuration of the heavens.” Specifically, they wrote that, in 1345, “at one hour after noon on 20 March, there was a major conjunction of three planets [Saturn, Mars and Jupiter] in Aquarius.” Adding to that, they noted, a lunar eclipse occurred around the same time.

Citing ancient philosophers such as Albertus Magnus and Aristotle, the Parisian medical scholars went on to connect the dots between planets and pestilence: “For Jupiter, being wet and hot, draws up evil vapors from the earth and Mars, because it is immoderately hot and dry, then ignites the vapors, and as a result there were lightning, sparks, noxious vapors and fires throughout the air.”

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Terrestrial winds, they went on, spread the noxious airs widely, smiting down “the life force” of anyone who ingested it into their lungs: “This corrupted air, when breathed in, necessarily penetrates to the heart and corrupts the substance of the spirit there and rots the surrounding moisture, and the heat thus caused destroys the life force, and this is the immediate cause of the present epidemic.”

A few centuries later, those noxious vapors were given another label: “miasma.” If it smelled bad, people reasoned, it must carry disease. That explains why, during the plague of 1665, some doctors donned beak-shaped masks filled with sweet-smelling flowers—to protect themselves from infection.

And never mind that playwright and poet William Shakespeare, like other Londoners of the early 1600s, bathed infrequently, and lived among rats, filth, fleas and sewage-filled street gutters. He, too, thought plague was an atmospheric thing. And taking the heavenly explanation even further, he wrote that malaria, a separate epidemic caused by swamp mosquitos along the Thames River, was caused by the sun steaming up swamp “vapors.”

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Pandemics have long bred prejudice and mistrust, and fueled longstanding biases, as traumatized communities have looked to blame others as unclean or malicious spreaders of disease.

Throughout medieval Europe the plague became an excuse to scapegoat and massacre Jewish people. Medieval Christian mobs attacked Jewish ghettos with virtually every wave of the disease, claiming that Jewish citizens poisoned wells and conspired with demons to spread the disease. In one pogrom, 2,000 Jews were burned alive in the city of Strasbourg on February 14, 1349.

Meanwhile, in the 19th and early 20th centuries, cholera sweeping across Europe became the subject of wild class-based conspiracy theories, as poor and marginalized people accused the ruling elite of ruthlessly working to cull their ranks by spreading the disease and deliberately poisoning them. From Russia to Italy to the United Kingdom, scores of riots followed, with members of the police, government and medical establishments murdered, and hospitals and town halls destroyed.

In the absence of scientific certainty, pandemics have often inspired people to grasp at answers based on whatever they immediately observe around them. With the Russian flu of 1889, bizarre theories evolved quickly into widely disseminated rumors. One newspaper, The New York Herald, speculated that the flu could travel on telegraph wires, after a large number of telegraph operators seemed to contract the disease. Others hypothesized that the flu may have arrived on letters from Europe, since mail carriers had begun to fall ill. In Detroit, when bank tellers began to get sick, some jumped to the conclusion that they'd caught it from handling paper money. Other rumored culprits included dust, postage stamps and library books.

Eventually, science began to see the unseen, and to explain why people dropped dead by the thousands. Of course, there were some plague-related issues that would always require a higher power. During the Middle Ages, it was believed that sneezing not only spread Black Death but caused a person to expel their soul. Hence, “God Bless You!”