A novel response to an outbreak of infectious syphilis in Christchurch, New Zealand.

During 2012, Christchurch experienced a dramatic increase in cases of infectious syphilis among men who have sex with men. This was accompanied by some novel trends; notably, the acquisition of infection in a younger age group, with local sexual contacts, commonly via the use of social media. This study is a report on an approach to case identification and public health communication as a component of a multifaceted outbreak response.