Syphilis is a sexually transmitted bacterial infection caused by the bacterium Treponema pallidum. The most common way syphilis spreads is through contact with an infected persons sore during sexual activity. The bacteria enter the body through minor cuts or abrasions in the skin or mucous membranes. Syphilis can also be transmitted from an infected mother to her unborn child. Syphilis is contagious during its primary and secondary stages, and sometimes in the early latent period.

Risk factors for acquiring syphilis include engaging in unprotected sex, having sex with multiple partners, being a man who has sex with men, and being infected with HIV, the virus that causes AIDS.

If left untreated, syphilis can lead to damage throughout the body, including small bumps or tumors, neurological problems, and damage to the heart and blood vessels, brain, and nervous system. Syphilis also increases the risk of HIV infection and can cause problems during pregnancy.

To prevent syphilis, it is recommended to abstain from sex. If sexually active, using condoms correctly every time can reduce the risk of getting or giving syphilis. However, syphilis transmission can occur with lesions not covered by a condom.