Syphilis is a sexually transmitted disease caused by the Treponema pallidum bacterium. This bacterium has an incubation period of two to four weeks, or even up to three months. The disease can be treated, but if left untreated, it may be dangerous to many systems of the body, such as the circulatory and nervous systems. Furthermore, an expectant mother with syphilis may transmit it to her unborn child, resulting in congenital syphilis.