syphilis (sif'ulis) [key], contagious sexually transmitted disease caused by the spirochete Treponema pallidum (described by Fritz Schaudinn and Erich Hoffmann in 1905). Syphilis was not widely recognized until an epidemic in Europe at the end of the 15th cent. Some medical historians have proposed that syphilis first appeared in Spain among sailors who had returned from the New World in 1493, while others have concluded from archaeological evidence that it probably originated in the Old World but may have been confused with leprosy. A study (released in 2008) that examined the evolutionary relationships among Treponema bacteria supported the idea that the spirochete originated in the New World, with some researchers suggesting it may have mutated into a sexually transmitted disease in Europe.
