1. British Association for Sexual Health and HIV:www.BASHH.org(last accessed June 2014).
2. Centers for Disease Control and Prevention (CDC):www.cdc.gov(last accessed June 2014).
3. BUPA fact sheet:http://www.bupa.co.uk/individuals/health‐information/directory/s/syphilis.
4. Centers for Disease Control and Prevention fact sheet:http://www.cdc.gov/std/syphilis/STDFact‐Syphilis.htm.