Treponemes are members of the family Spirochaetaceae, which also contains Borrelia and Leptospira. Although most treponemes do not cause disease in human beings, a few cause substantial morbidity. This chapter briefly reviews the clinical manifestations and treatment of syphilis in adults and the nonvenereal treponematoses, yaws, pinta, and bejel.
Transmission and stages of infection
Syphilis is primarily transmitted through sexual contact with infectious mucocutaneous lesions in primary and secondary syphilis. Mother-to-child transmission can occur from transfer of the spirochete through the placenta or, less commonly, from contact with infectious exudates or blood through the birth canal. Transmission of syphilis through blood products is now rare due to routine screening of donors.
Like other treponemal diseases, the clinical manifestations of syphilis are divided into early and late stages. Early syphilis is further divided into primary, secondary, and early latent stages. During the latent syphilis stage, patients have positive serologic tests for syphilis but no other signs of disease. The Centers for Disease Control and Prevention (CDC) classifies patients in the latent stage as having early syphilis if they acquired infection during the preceding year. Otherwise, persons with latent disease are classified as having either late latent syphilis or latent syphilis of unknown duration. Although clinical staging is useful for diagnosis and treatment, it is also imprecise; overlap between stages is relatively common.