Introduction In the Netherlands, approximately 90% of all infectious syphilis (syphilis) and 70% of all new HIV infections are among men who have sex with men (MSM). As the relation between syphilis and HIV is characterised by a bidirectional synergy, we assessed syphilis trends among MSM stratified by HIV status.

Methods The national STI/HIV surveillance contains epidemiological, behavioural and clinical data from STI clinics, which provide low threshold STI/HIV testing and care for high-risk groups. We descriptively examined syphilis positivity rates between 2007 and 2014.

Results The number of MSM consultations increased each year from 11,048 in 2007 to 29,939 in 2014. Of all MSM, 83% were HIV-negative. The number of syphilis diagnoses was lowest in 2011 (n = 426) and highest in 2014 (n = 693), of which around 40% was among HIV-infected MSM each year. Among known HIV-infected MSM, the syphilis positivity rate decreased between 2007 (12.3%) and 2011 (4.5%), followed by an increase in recent years (2014: 6.6%). Among MSM newly diagnosed with HIV, this trend was roughly similar to that of known HIV-infected MSM. Among HIV-negative MSM, the syphilis positivity rate decreased between 2007 (2.8%) and 2011 (1.4%), and remained stable thereafter.

Conclusion The observed rebound in syphilis rates in a high-risk group of HIV-positive MSM is concerning at individual level, given the adverse effects on both syphilis and HIV disease progression. At public health level, this is worrisome as syphilis facilitates transmission and acquisition of HIV. Therefore, syphilis infection could be indicative to offer HIV pre-exposure prophylaxis (PrEP) among HIV-negative MSM. On the other hand, offering PrEP to a high-risk core group could promote syphilis transmission if it leads to reduced perceived vulnerability and subsequent increased risk behaviour, as seen after the introduction of cART.

Disclosure of interest statement The authors declare that they have no competing interests.