Epidemiology of syphilis in the Nepean and Blue Mountains Local Health District between 1 October 2009 and 30 September 2019.

Background: Syphilis is a nationally notifiable sexually transmitted infection (STI). Rates of syphilis notifications have been on the increase in Australia. Given these increases, we wanted to study the epidemiological trends of syphilis notifications in the Nepean Blue Mountain Local Health District (NBMLHD) over a ten-year period across different healthcare settings.

Methods: All syphilis notifications in residents in the NBMLHD in the ten-year period between 1 October 2009 and 30 September 2019 were included in the study. Separate analyses were performed for all syphilis notifications, as well as for infectious syphilis and for syphilis acquired > 2 years ago or of unknown duration. We described age distribution and demographic profile and risk factors of all syphilis notifications. Notification trends were studied and crude incidence rates were calculated. Notifications were stratified by stage of syphilis, sex, and geographical location.

Results: In the study duration, a total of 342 notifications of syphilis were received. Of these, 187 were infectious syphilis and 155 were related to infections acquired > 2 years ago and/or of unknown duration. The majority of notifications were in men: 281 (82%). Overall, syphilis notifications increased over the ten-year study period. The crude incidence rates for infectious syphilis were significantly higher in the second five-year period overall (7.78/100,000 population per year compared to 5.28/100,000 population per year; incidence rate ratio (IRR): 1.47; 95% confidence interval (95% CI): 1.10-1.97; p < 0.01), as well as for males (14.44/100,000 population per year compared to 9.7/100,000 population per year; IRR: 1.49; 95% CI: 1.09-2.03; p < 0.01). There were significant increases in syphilis notifications in males < 35 years of age, from 39 such notifications in the first five-year period (27.5% of all syphilis notifications in this period) to 83 notifications in the second five-year period (42.1% of all notifications in this period), p < 0.05.

Conclusion: In keeping with national trends, notifications in our study increased. Significant increases were noted in notifications among males under 35 years of age. This supports the continued investment in sexual health promotion activities aimed at young sexually active men. Expansion of screening activities to include women and older people would help detect any increase in cases in these groups. Increase in engagement with general practitioners will support them to provide opportunistic STI screens to sexually-active attendees. National screening recommendations remain applicable to this population.