We analysed syphilis cases by year of diagnosis, age, sex, area of residence, and transmission group.Self-reported data on sexual risk behaviours and diagnoses of HIV and syphilis among MSM were collected during four waves of a behavioural MSM survey in 2003, 2007, 2010, and 2013.
In Germany, syphilis diagnoses have been notified anonymously on the basis of the Protection against Infection Act in Germany  since 2001 by laboratories, with physicians inserting relevant clinical information.
Syphilis cases are defined as cases diagnosed by direct detection of T.
This subgroup is less affected by the change in recruitment methods.
The sample sizes of the surveys were: 4,750 in 2003, 8,170 in 2007, 54,387 in 2010, and 16,734 in 2013.
Citation style for this article: Jansen K, Schmidt AJ, Drewes J, Bremer V, Marcus U. Especially in western countries, sharp increases in numbers of syphilis infections were observed [1-4].