A review of sexually transmitted infections (STIs) in men who have sex with men (MSM) since the 1960s and an analysis of possible future trends suggest that incidence will likely remain high in the near future. But there are grounds for hope that human papillomavirus (HPV) vaccination and pre-exposure prophylaxis (PrEP) use will engage more men in care and regular screening.
Mark Richard Stenger of the Centers for Disease Control and Prevention, Stefan Baral of the Johns Hopkins Bloomberg School of Public Health and colleagues recently published their potted history and future gazing exercise in the journal Sexual Health.
Reviewing the medical literature of the past half century, the authors found that an excess burden of STIs in MSM was already being noted in several cities internationally by the mid-1960s. Data collection and public health surveillance were sporadic and incomplete, but the available evidence suggests that STIs were hyperendemic among MSM by the close of the 1970s.
The rapid and devastating spread of HIV among MSM in the 1980s had significant consequences for sexual behavior and sexual networks. Behavioral changes, including fewer sexual partners, slower rates of partner exchange and increased condom use, were spontaneously adopted by MSM in response to AIDS. At the same time, men who had sometimes occupied central positions in sexual networks died or became less sexually active due to AIDS-related illnesses. These network effects contributed to slowing the spread of STIs in the AIDS era.
The HIV treatment era, from the mid-1990s onwards, has seen a resurgence of STIs, especially among men with diagnosed HIV. The incidence of gonorrhea, syphilis and other infections has returned to pre-HIV levels.
Mark Stenger and colleagues say that this has been due to a combination of factors: "A highly visible decrease in HIV/AIDS-associated morbidity among those infected, emerging optimism with respect to HIV transmission, and an overall prevention fatigue among MSM, appeared to be leading to increased sexual risk-taking as evidenced by greater numbers of MSM being diagnosed with STIs."
And what for the future? They identify ten current and future trends:
- The incidence of STIs is likely to continue to rise. Given their assessment of current trends, the authors believe there is little reason to be sanguine looking towards 2020. The current high prevalence and incidence of many infections must be considered alongside MSM's "well-founded optimism" regarding new ways to prevent HIV transmission. But it would be simplistic and reductionist to explain everything in terms of individual risk behavior.
- Network factors will have a significant impact on STI incidence. In urban areas characterized by dense sexual networks, population churn and a high prevalence of anonymous partnerships, the conditions are right for ongoing transmission of STIs to be sustained. More interventions to reduce STIs should be focused on network, rather than individual, factors.
- "A conceptual decoupling of HIV and STI prevention." With the arrival of PrEP and greater awareness of the impact of HIV treatment on infectiousness, this separation of prevention strategies is already underway. Attitudes towards asymptomatic STIs with few long-term health consequences may be evolving; interventions should focus more specifically on those infections that have a more significant impact on health, such as HPV and syphilis.
- PrEP may encourage MSM to develop an ongoing relationship with providers. The regular monitoring that PrEP requires may help normalize engagement with care. MSM taking PrEP will have repeated screening for STIs, allowing infections to be diagnosed and treated early. While the number of documented cases may initially rise, reductions in the duration of infectiousness may help reduce incidence in the long term.
- Increasing detection of gonorrhea and chlamydia in the rectum and pharynx. As providers and MSM become increasingly aware of the value of screening in non-genital sites, including in the absence of symptoms, an increasing proportion of infections will be detected. This will make data difficult to interpret: Will observed increases in infections reflect true increases in incidence, an artifact of enhanced screening or a combination of both?
- Greater difficulty in treating and controlling gonorrhea. The emergence of antimicrobial-resistant strains raises the prospect of persistent and difficult-to-treat gonorrhea infections, potentially across multiple anatomic sites. They may represent an unacceptable future burden in terms of quality of life, as well as in terms of health care costs. Resistance is also making expedited options for partner treatment ineffective.
- Better control of HPV and genital warts. In areas where the uptake of HPV vaccine is robust in both girls and boys, the burden of genital warts in the general population has fallen considerably. Where strong vaccination programs are implemented, it is plausible that they could have a similar impact on genital warts, anal warts and HPV-associated cancers in MSM.
- The spread of novel sexually transmitted pathogens into networks of MSM. The authors note that, already in the 1970s, among MSM there were case reports of Lymphogranuloma venereum (LGV), viral hepatitis and other pathogens not usually associated with sexual transmission. Currently, we should be vigilant to the introduction of Zika and Ebola viruses into MSM networks, as the conditions for rapid spread exist.
- Better surveillance of sexually transmitted infections in MSM. While data from earlier decades were often limited and incomplete and generally based on non-representative clinic populations, the public health evidence-base has improved significantly over the past decade. There is better recording of people's sexual orientations and gender identity, as well as efforts to estimate the size of sexual minority populations.
- The increasing social acceptance and integration of sexual and gender minorities will have effects that are difficult to predict. These structural changes could impact sexual behaviors and the dynamics of transmission. These changes may be most profound in other parts of the world.