Syphillis is a sexually transmitted infection (also known as a sexually transmitted disease or STD) that usually start off with a single sore on the genitals, mouth, or rectum. It is spread through genital or oral contact with the sore.
Syphilis is a bacteria. Once it is contracted, it can lie dormant in the body of long periods of time (years or even decades) prior to the patient displaying symptoms. Early stage syphilis is cureable with penicillin (possibly with as little as one shot). When syphilis is not treated, irreversible damage to the heart and brain can occur and it can be fatal.