The cause of syphilis is a bacterium called Treponema pallidum. The most common route of transmission is through contact with an infected person’s sore during sexual activity. The bacteria enter your body through minor cuts or abrasions in your skin or mucous membranes. Syphilis is contagious during its primary and secondary stages, and sometimes in the early latent period.
Less commonly, syphilis may spread through direct unprotected close contact with an active lesion (such as during kissing) or through infected mothers to their babies during pregnancy or childbirth (congenital syphilis).
Syphilis can’t be spread by using the same toilet, bathtub, clothing or eating utensils, or from doorknobs, swimming pools or hot tubs.
Without treatment, syphilis can lead to damage throughout your body. Syphilis also increases the risk of HIV infection and, for women, can cause problems during pregnancy. Treatment can help prevent future damage but can’t repair or reverse damage that’s already occurred.