syphilis (sif'ulis) [key], contagious sexually transmitted disease caused by the spirochete Treponema pallidum (described by Fritz Schaudinn and Erich Hoffmann in 1905). Although some medical historians believe that syphilis first appeared in Spain among sailors who had returned from the New World in 1493, others have concluded from archaeological evidence that syphilis probably originated in the Old World but may have been confused with leprosy. It was not widely recognized until an epidemic in Europe at the end of the 15th cent.
