Use of gay app and the associated HIV/syphilis risk among non-commercial men who have sex with men in Shenzhen, China: a serial cross-sectional study.

App-using NcMSM are more likely to have sexual risk behaviours as well as risk-reduction behaviours such as consistent condom use and HIV testing. Scaled-up and innovative venue-based HIV interventions are warranted for these high-risk MSM frequent social venues with less condom use and fewer HIV tests. Meanwhile, gay app should alternatively serve as an intervention and education platform for the MSM hard-to-reach via venue-based approaches.