Syphilis is a bacterial infection usually spread by sexual contact. The disease starts as a painless sore — typically on your genitals, rectum or mouth. Syphilis spreads from person to person via skin or mucous membrane contact with these sores.
After the initial infection, the syphilis bacteria can lie dormant in your body for decades before becoming active again. Early syphilis can be cured, sometimes with a single injection of penicillin. Without treatment, syphilis can severely damage your heart, brain or other organs, and can be life-threatening, or be passed from mother to an unborn child.