The sexual landscape has changed. Sexual networks are now different. Gay and bisexual men who don't adjust to these circumstances could soon get a nasty surprise… People often think of STIs at a micro or personal level – "I haven't changed how I have sex therefore my risks of acquiring an infection are the same as they've always been". But another way to understand patterns of STI acquisition (and therefore individual risk) is to take a macro or population perspective. That is, what other people are doing, and who they're doing it with. STIs thrive in certain conditions and not in others. After being introduced into a population, STIs survive in a community of linked people if there is a small core of very sexually active individuals. These men act as an engine room of epidemics, because the sexual connections they forge make it easier for STIs to spread quickly and deeply through the network. It's the size of this core, and the way they're linked to other men, that helps shape the course of a sexually transmitted disease epidemic. It determines the pathways of transmission; where it will meet resistance (high levels of condom use, low rates of sexual partner change, early diagnosis) and where the weak points are (low levels of condom use, rapid partner change, late diagnosis or undiagnosed infections). In the 1970s and early eighties, STIs were rife among gay and bisexual men. In 1984, 38% of a cohort of gay men in Sydney reported a history of syphilis alone. From the mid-1980s and early nineties, gay communities took up condoms against HIV in one of the most effective public health responses in history. Not surprisingly, condoms partially acted as a "circuit breaker" for other STIs as well, and rates of most STIs declined through this period. In other words, STIs exploited gay men's high sexual connectivity in the seventies, but the uptake of safe sex helped prevent the same STIs from repeating this assault on our communities a decade later. As we know, many men who were both highly sexually connected and who didn't use condoms for anal sex also acquired HIV - rates of HIV went from zero to almost 50% in just 5 years among a cohort of high-risk homosexual men in San Francisco. Before the arrival of new treatments for HIV in 1997, many men who'd had a lot of unsafe sex became unwell and died. Thinking about STI transmission from an ecological perspective, the high mortality of men in these core groups removed them from the sexual network and effectively shrank the size of the epidemic's "engine". Rises in condom use, and the withdrawal of many highly sexually connected gay men from sexual networks because of AIDS, were largely why STI epidemics were declining among MSM during those latter years. So how have things changed? What does the landscape look like now? Can this help explain why we're seeing resurgences of STIs in homosexual men around the world, including New Zealand? Post-1997, the new HIV treatments (which have been a great success in terms of improving positive men's lifespan and wellbeing) and Internet dating (which increases choice and the frequency of exchanges in the sexual marketplace) have without doubt combined to create a new STI environment among gay and bisexual men. Men infected with HIV are living longer and are having active sex lives. The Internet is creating new opportunities for hooking up; enlarging the core group, and altering how these men locate and mix with other, less sexually active men. It potentially completely rearranges the patterns of connectivity between men who are infected with an STI and men who are susceptible to infection. STIs adore these conditions - it's as if we've built more bridges and superhighways and added new on ramps and off ramps. With Internet networking and HIV treatments here to stay, the implications for individual and community health are the same: Everyone needs to be more vigilant with condoms and sexual health checks, whether you're positive or negative. This is especially true for energetic guys who have a lot of sexual partners – the "fast lane" lads. But it also applies if you stick to a small number of partners, because it's practically impossible to know whether your partner's partner's partner is very sexually active too. In fact no matter which end of the sexual partnering spectrum you're at, you might unwittingly be only two degrees of separation from a guy whose preferences are quite different from your own. Greater vigilance isn't a moralistic response. It's about self-preservation – acknowledging how STIs spread through sexual networks, and how we can adjust to thwart them. This is a difficult message to sell, because the consequences of HIV infection aren't as visible these days, and men often won't reveal that they've had (or have) an STI. In the 2006 Gay Auckland Periodic Sex Survey (GAPSS), 40.8% of men reported a lifetime history of at least one STI, with 8.0% reporting an STI in the previous 12 months. The most common of the recent STIs were gonorrhoea and chlamydia (both 3.3% in the last year), with around 1% reporting syphilis. On the bright side, gay and bisexual men are generally diligent about sexual health checks – 43.2% claimed to have had one in the previous 12 months, being lower among men with fewer sexual partners, men aged 40 and over, and Asian men. As we head into summer, you can make a big dent in your own risk and the risk of everyone who'll ever be sexually connected to you if you take two simply precautions – use a rubber for anal sex, and go for a full sexual health check. No matter who you are… Peter Saxton Peter Saxton, Senior Researcher at the NZAF Research, Analysis and Information Unit, delivered a plenary paper at the NZ Sexual Health Society Conference in August on the re-emergence of STIs and HIV infection among MSM in the post-HAART, post-Internet-dating environment. Slides from his conference paper can be viewed at this link: http://nzshs.org/content/nzshs/24/2-24.htm The report of the 2006 Gay Auckland Periodic Sex Survey can be viewed here: http://www.nzaf.org.nz/files/2006%20GAPSS%20Report.pdf Peter Saxton - 13th December 2007