Syphilis may well cause death. “If not treated, syphilis can cause serious effects such as damage to the heart, aorta, brain, eyes, and bones. In some cases these effects can be fatal.” (Wikipedia)
Oh, haha, it was just a joke, because Nietzsche, the dude who said, “That which does not kill you makes you stronger,” had syphilis during his final years, and went crazy. He was a vegetable throughout the 1890’s. I wonder if he still agreed with his aphorism at the end. I wasn’t being serious, but thanks, mgus.