Factors associated with syphilis incidence in the HIV-infected in the era of highly active antiretrovirals. Medicine
Shilaih et al. aimed to examine the factors that affect syphilis incidence in the Swiss HIV Cohort Study. The incidence rate was 26.8 cases per 1000 person-years for men who have sex with men (MSM), 1.3 for intravenous drug users, and 1.8 for heterosexuals. There was a significant increase of syphilis incidence over time, however, without clear elevation directly after the introduction of the Swiss Statement in 2008. The MSM population was most affected by syphilis and accounted for 92% of incident cases (92%). Unexpectedly, nevirapine was associated with lower syphilis incidence in the multivariate model, whereas condomless sex and younger age were associated with higher syphilis incidence. Testing frequency higher than the recommended once a year routine testing was associated with a 2-fold higher risk of acquiring syphilis.
In conclusion, this study demonstrates that syphilis incidence has been continuously increasing in recent years with the main driver being high-risk behavior, namely condomless sex. This observation entails targeted interventions and frequent screening of high-risk populations. Antiretroviral treatment generally does not provide a protective effect against syphilis. The intriguing protective association of nevirapine against syphilis incidence demands further investigation.