Epidemiology and prevention of sexually transmitted infections in men who have sex with men at risk of HIV

Summary

Since 2012, the increasingly widespread promotion and uptake of HIV treatment as prevention and pre-exposure prophylaxis in men who have sex with men has been associated with increased sexually transmitted infections (STIs). However, numbers of STI cases have been rising for more than 20 years and the introduction of biomedical HIV interventions cannot explain the majority of the rises in STIs. The increases appear to have occurred mostly because of gradual changes in behaviour over many years, coupled in some settings with more condomless anal intercourse, and as a result of the increased screening for previously undetected asymptomatic infections. If control of STIs is to be improved, then a far greater emphasis on increased use of existing effective STI control strategies will be required, in addition to the investigation of new interventions. Central to effective STI control is accessible clinical care and screening services, which are currently inadequate in most settings. Insufficient action carries a risk of increased STI epidemics, including of newly resistant organisms.

Introduction

Two biomedical interventions have been introduced in the past decade to prevent HIV, treatment as prevention (TasP) and pre-exposure prophylaxis (PrEP), which have proven to be remarkably effective.1, 2 To our knowledge, no cases have been reported of HIV transmission from an individual on HIV treatment with an undetectable viral load, and HIV-uninfected homosexual and bisexual men who have sex with men (MSM) who are adherent to PrEP are nearly 100% protected from acquiring HIV.¹ In the mid-2010s, these biomedical interventions have translated into dramatic reductions in new HIV infections among MSM at the population level in places such as San Francisco, CA, USA, London, UK, and Melbourne and Sydney, Australia.3, 4, 5, 6

In contrast to the reductions in HIV incidence, trends in bacterial sexually transmitted infections (STIs) show a different temporal pattern. The notification rates for STIs fell with the arrival of HIV in the 1980s, and then in about 2000 began to gradually rise, with an acceleration in frequency around 2010 (figure 1; appendix pp 2–5).7, 8, 9 The reasons for these rises are complex. The changes in the perception of the severity of HIV and AIDS over the past 30–40 years might have contributed to behaviour changes (ie, increases in partner numbers and decreases in condom use) and might explain some of the STI rises among MSM.⁷ For example, an Australian study showed a large increase in condomless anal sex with casual partners between 1998 and 2006.¹⁰ However, many other factors might also be important, including changes in mixing patterns within risk groups, use of smartphone dating applications, group sex, recreational drug use, and access to health care.⁷

The rises in STIs are of concern for many reasons. STIs are associated with a large financial burden worldwide. For example, in the USA, STIs cost the health-care system approximately US$16 billion a year, and cause individuals severe symptoms and complications.¹¹ The rapid rise in syphilis infection has led to the re-emergence of congenital syphilis in some areas.¹² Gonorrhoea is at risk of becoming resistant to the last first-line antibiotic treatment (dual treatment with ceftriaxone and azithromycin), prompting its elevation to an urgent resistance threat by the US Centers for Disease Control and Prevention and a global threat by WHO.13, 14 Both organisations have indicated that decreasing gonorrhoea prevalence is a key strategy to minimise rises in resistance.

In this this Review, we describe the changes in incident STIs among MSM that have occurred in the past 20 years, and in factors that might be contributing to these changes, before providing some steps that could be taken to reduce STIs in the present context of improved control of HIV.