In A Nutshell
From its first appearance in Europe in 1495, syphilis was a fast-acting disease which devastated the bodies of sufferers and killed them within the space of six months. By 1546, however, it had become a slow-acting disease whose symptoms could be felt for decades. This change came about because the bacteria which caused the disease had evolved, seemingly realizing that by leaving sufferers alive for longer, it would ensure the survival of its species for much, much longer than previously possible.
The Whole Bushel
Of all the diseases to have ravaged humankind, syphilis is undoubtedly one of the worst. For starters, epidemiologists have (so far) been unable to work out precisely how many people have died as a result of it throughout history, simply because there have been so many outbreaks. Secondly, and more troubling, the scant historical records of these outbreaks reveal an uncomfortable fact about the disease: that in the few years between 1495 and 1546, syphilis evolved to become a more efficient killer.
According to the 1997 Pulitzer Prize-winning book Guns, Germs, and Steel by Jared Diamond, a professor of Geography and Physiology at the University of California, contracting the disease was originally a horrific pain-filled death sentence. Sufferers—who would mercifully only live for six months—would be engulfed from head to toe in large liquid-filled pustules referred to as “purple flowers,” all while their flesh literally melted down to the bone. This date of 1495 is derived from the date of the first recorded outbreak of syphilis in Europe, which struck a group of soldiers in Naples before forging a deadly trail across the world.
However, by 1546, as if the disease “realized” that it was killing its victims too quickly, the severity of these symptoms (as well as the speed of their onset) had vastly reduced to create the form of syphilis that we see today.
Why? Because just as all humans are programmed to ensure the continued survival of the species through reproduction, the bacteria responsible for causing syphilis—Treponema pallidum—is the exact same, the only difference being that whereas we accomplish this through sexual reproduction, bacteria reproduce by infecting person after person after person. The speed with which syphilis initially killed didn’t allow enough time for its victims to pass the disease onto others.
Thus, by rapidly evolving into a disease whose side effects can last for decades, syphilis can spread much, much further in its quest to avoid extinction. Whoever said that the circle of life was always a good thing, eh?
Show Me The Proof
Guardian: Syphilis, sex and fear—How the French disease conquered the world
Guns, Germs And Steel, Jared Diamond
Syphilis: CDC Fact Sheet