Cold chills. Throbbing head. Muscle aches. Fatigue. The sweats. If you experienced those symptoms today, you’d probably just regret putting off your flu shot this year. But if those things cropped up in 1485, your family would likely start planning your funeral. In the late 1400s and early 1500s, these symptoms almost certainly meant you had fallen victim to the mysterious “English Sweating Sickness,” a disease that struck without warning and could kill within hours.

From 1485 though 1551, five epidemics of this terrifying disease swept through England, and once through Europe, with mortality rates from 30 to 50 percent. The illness seemed to be prevalent among upper class males, so the royals and their cohorts were particularly affected. Because of this fact, the sweating sickness may have changed the course of history.

In 1502, just six months after his marriage to Catherine of Aragon, Arthur, Prince of Wales, died suddenly at the age of 15. Though an official cause of death wasn’t recorded, some historians believe Arthur was another sweating sickness fatality. As the oldest male child in the family, Arthur would have ascended to the throne if he hadn’t succumbed to the illness. His younger brother, Henry, Duke of York, ended up taking the crown instead. You probably know him better as Henry VIII, who married his brother’s widow seven years later. She was the first of his six wives, of course.

Though it’s been difficult for modern-day doctors and scientists to trace the origins of the English Sweating Sickness, there’s been educated speculation that it was the result of hantavirus pulmonary syndrome (HPS), which wasn’t even recognized until 1993. Spread by certain rodents, HPS has the exact same symptoms and a similar mortality rate: 38 percent.

But even if 16th century doctors were aware that the English Sweating Sickness was really HPS, there’s little they could have done—to this day, there is no cure or vaccine that will stop it. The CDC’s advice? Avoid rodent infestations, which was a lot harder to do in 16th century England.