Syphilis is a bacteria caused by Treponema pallidum (T. pallidum) spirochaete bacterium. Commonly associated with the Sexually Transmitted Diseases (STD), syphilis bacterial infection can get passed on or transmitted through blood transfusion, mother to a child, and individuals living in depressed areas or with poor hygiene. Syphilis is endemic and contagious.
Symptoms may show or not and can live for years without signs. So, you can get infected by the T. pallidum bacterium without having any sexual contacts.