SYPHILIS REINFECTION IN NEW SOUTH WALES, 2014-2021

Abstract

Intro: Syphilis is a growing health problem internationally, with repeat syphilis infections representing a key diagnostic and disease control challenge. Reinfections are more likely to be asymptomatic and thus harder to detect without enhanced screening. Higher rates of reinfection have implications for epidemic control and are associated with increased congenital syphilis, with between 8.4% and 22.1% of congenital syphilis cases due to maternal reinfection or treatment failure. In Australia, syphilis infection is a nationally notifiable disease. In New South Wales (NSW) syphilis is notifiable on laboratory diagnosis and enhanced surveillance data is routinely collected from diagnosing clinicians. We sought to quantify and describe reported syphilis reinfections in NSW between 2014 and 2021. Methods: All notifications of infectious syphilis in NSW with symptom onset between 01 January 2014 and 31 December 2021 were included in the cohort, with the unique person identifier used to identify single infections and reinfections. We described the cohort using demographic, exposure, and clinical factors. Findings: Our cohort comprised 8,862 individuals with a recorded infectious syphilis notification during the study period, with reinfections identified in 1,152 people (range of notifications per person between 1 and 7). The cohort was 93.7% male, median age 36, and 93% residing in major metropolitan areas. Of the males with sexual history information available, 80.7% report same-sex sexual activity. 51.9% of infections were symptomatic. There were 10,299 confirmed or probable infectious syphilis notifications among the cohort; 14% (1,437/10,299) were reinfections in previously infected and treated individuals. Only 34.5% of reinfections were detected on symptom-prompted testing, compared to 45.7% of first infections. Conclusion: Syphilis infections are concentrated in males who reside in major metropolitan areas in NSW. Many infections were not symptomatic, highlighting the need for enhanced screening in at-risk populations. Further analyses on median time to reinfection and risk factors for more rapid reinfection are planned.