1. Centers for Disease Control and Prevention: STD Surveillance 2006, National Profile. Available at http://www.cdc. gov/std/stats/syphilis.htm . Accessed August 2008.
2. Centers for Disease Control and Prevention: Primary and secondary syphilis—United States, 2000–2001. MMWR Morb Mortal Wkly Rep 2002, 51:971–973.
3. Heffelfinger JD, Swint EB, Berman SM, Weinstock HS: Trends in primary and secondary syphilis among men who have sex with men in the United States. Am J Public Health 2007, 97:1076–1083.
4. Centers for Disease Control and Prevention: Transmission of primary and secondary syphilis by oral sex-Chicago, Illinois, 1998–2002. MMWR Morb Mortal Wkly Rep 2004, 53:966–968.
5. Simms I, Fenton KA, Ashton M, et al.: The re-emergence of syphilis in the United Kingdom: the new epidemic phases. Sex Transm Dis 2005, 32:220–226.