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.
Syphilis rates in the United States have been declining among women since 2010, but rising among men, particularly men who have sex with men. The genital sores associated with syphilis can make it easier to become infected with HIV, the virus that causes AIDS.