Syphilis is a sexually transmitted disease (STD) caused by an infection with bacteria known as Treponema pallidum. Like other STDs, syphilis can be spread by any type of sexual contact. Syphilis can also be spread from an infected mother to the fetus during pregnancy or to the baby at the time of birth.n secondary syphilis, the infection has spread throughout the body, so other symptoms may be associated with the skin manifestations. Fever, enlarged lymph nodes, fatigue, weight loss, hair loss, headaches, and muscle aches have all been reported in the secondary stage of syphilis.