An illness caused by infection with bacteria and spread mainly by contact with genitals or body fluids that starts as a painless sore.

Syphilis is an infection by Treponema pallidum bacteria. The bacteria usually spread from person to person during sexual contact and start as a painless sore. Without treatment, syphilis can lead to damage throughout the body.

Syphilis develops in stages, and symptoms vary with each stage. After the initial sore heals, a rash may appear. Untreated syphilis can damage the nervous system, organs, bones and joints as well as blood vessels and the heart.

Medicine that targets bacteria, called an antibiotic, treats syphilis.