Syphilis is a sexually transmitted disease caused by spiral-shaped bacteria called treponema pallidum. Syphilis is acquired during sexual contact with an individual already infected with the bacteria. The course of the disease caused by t. pallidum has four distinct phases: primary syphilis, secondary syphilis, latent syphilis, and advanced or tertiary syphilis.

Symptoms of primary syphilis crop up about three weeks after an individual acquires the causative bacteria. A small hard bump, followed by an ulcer (chancre) appears at the point of entry of the bacteria, usually on the penis in men or on the vulva, vagina, or cervix in women. This chancre lasts for about a month, during which time the individual is extremely contagious.

After the disappearance of the chancre, several months may pass, followed by a flu-like illness and rash. The individual during this phase is also extremely contagious, because of multiple lesions on within the mouth and on the genitalia.

Latent syphilis refers to the bacteria lying dormant within an individual's body, with no recognizable symptoms whatsoever. This phase can decades. During this phase, the body may overcome the bacteria, or the bacteria may take hold in multiple locations of the body, only to resurface as tertiary syphilis in the future.

Tertiary syphilis can occur in many different locations, but the worst results include insanity due to lesions on the brain, blindness, and severe destructive scarring lesions (called gumma) located in the bones, liver, spleen, heart, and skin. About 30% of all individuals with latent syphilis develop this serious, often fatal form of syphilis.

One of the most disturbing features of syphilis is its ability to cause disease in the babies of an infected mother. Symptoms of syphilis may be manifested in the newborn, or may remain latent, appearing later in life in the full-blown tertiary form.

All forms of syphilis are treatable with penicillin antibiotics, although tertiary syphilis may have already caused irreparable damage.