Syphilis is caused by the spirochete Treponema pallidum. Clinical syphilis usually is subdivided into primary, secondary, latent, and tertiary (late) stages. The primary stage begins after an average incubation period of 3-6 weeks (range, 1.5-13 weeks) and is manifested by the development of a primary stage shallow ulcer, or chancre, near the site of infection. […]