Syphilis on the rise among Singaporean men living with HIV
There is a steady annual growth in the incidence rate of syphilis in men living with HIV, according to a new Singapore study. Rates are consistently higher among men who have sex with men (MSM) than their heterosexual counterparts.
“[T]he increasing trend of incident syphilis in HIV-infected men observed in our study highlights the need for regular sexually transmitted infection (STI) screening and enhanced behavioural interventions in Singapore,” said researchers. “In order to alleviate the burden of syphilis coinfection in [people living with HIV (PLHIV)], concerted efforts to reduce risky sexual activity should target those identified to be at increased risk of STIs.”
In the 1,069 men living with HIV included, there were 266 incident cases of syphilis. The resulting incidence rate was 6.21 per 100 person-years of follow-up (PYFU). Each participant was followed-up for a median of 3.64 years. [Sex Trans Infect 2019;doi:10.1136/sextrans-2019-054163]
There was a significant increase in syphilis incidence over time, growing from 1.21 per 100 PYFU in 2010 to 10.09 per 100 PYFU in 2016. This was followed by a spike in the number of new cases, reaching 26.04 per 100 PYFU in 2017.
Stratifying according to sexual orientation showed that the rate of syphilis seroconversion was significantly higher among MSM than men who acquired the infection through heterosexual contact (9.00 vs 2.22 per 100 PYFU).
Temporal trends in incidence were similar in both groups, though MSMs showed consistently higher numbers (14.77 per 100 PYFU in 2016 to 35.85 per 100 PYFU in 2017 vs 2.67 per 100 PYFU in 2016 to 14.29 per 100 PYFU in 2017).
Multivariate Cox regression analysis showed that being diagnosed with HIV at a younger age (15–24 vs ≥45 years: adjusted hazard ratio [HR], 1.64, 95 percent CI, 1.05–2.56) or during more recent calendar years (2009–2011: adjusted HR, 1.96, 1.41–2.74; 2015–2017: adjusted HR, 7.94, 4.52–13.95), as well as being of Chinese ethnicity (adjusted HR, 1.82, 1.01–3.29), increased the risk of being diagnosed with incident syphilis.
HIV exposure via MSM vs heterosexual contact also emerged as a significant risk factor (adjusted HR, 3.29, 2.22–4.87).
“The reasons for the resurgence of syphilis are likely to be multifactorial,” said researchers. The greater availability of HIV antiretroviral therapy and pre-exposure prophylaxis therapy, for instance, may have changed risk perception and sexual behaviours. A better overall awareness of STIs and the importance of testing may have also led to a rise in the number of reported cases.
“In Singapore, specific national guidelines for syphilis testing in PLHIV do not yet exist,” they added, but the National Centre for Infectious Diseases recommends annual testing for those positive for HIV or who are at high risk.
“The results of this study supported alignment of regular syphilis screening in Singapore with international recommendations,” said researchers.