Syphilis is a venereal disease, or STD, that is unusual, unique in many ways. First of all, it is one of the few major diseases to have originated in the Americas, the New World, and carried back to Europe most likely by Columbus; Popularized by “guns germs and steel”, the infectious disease traffic was almost all the other way, most famously smallpox which decimated the Native Americans.

A second unusual characteristic is that it’s treatment(penicillin) is known, cheap, easy, and yet Syphillis infects millions of people yearly, most commonly to be sure in the developing world, but also large numbers in America where is helped by AIDS, and spread by men having sex with men.
A third unusual characteristic is that syphilis can mimic practically any disease. There are three stages. The first stage is a painless ulcer, usually on the genitals. After a few weeks, the second stage develops, showing a widespread rash and other symptoms. After a few more months, problems develop in the heart, brain, or growths ( gummas) in many other areas .
When I was in medical school we used to go to an old peoples home to listen for aortic regurgitation, and observe the neurologic symptoms of syphilis patients. Syphilis is still a cause of aortic insufficiency, if untreated.
Treponema pallidum, The causative agent, is also unusual. It has a very small geome, and has many missing cellular mechanisms, making it dependent upon Homo sapiens, it’s only known Reservoir. The fragile but very active organism will die in a few hours outside of its human host. Like it’s confederate,AIDS, The infection can easily spread from mother to child with devastating consequences. It is one of the major diseases for which pregnant mothers are tested.
Syphilis is one of the best arguments for being monogamous. If this can’t be, remember that syphilis is easily treatable, and that you should report any unusual illnesses to your doctor.