From the US paper:
Results: Sixty-eight percent [95% confidence interval (CI) 58–78) of HIV transmissions were from main sex partners because of a higher number of sex acts with main partners, more frequent receptive roles in anal sex with main partners, and lower condom use during anal sex with main partners. By sex type, 69% (95% CI 59–79) of infections were from receptive anal intercourse, 28% (95% CI 19–38) were from insertive anal intercourse, and 2% (95% CI 0–5) were from oral sex. The model-based estimated HIV incidence rate was 2.2% (95% CI 1.7–2.7) per year. Sensitivity analyses demonstrated estimates of transmission from main sex partners as low as 52% (95% CI 41–62) and as high as 74% (95% CI 68–80).Though this will probably shock a lot of people, I think a lot of people who work in the field will not be surprised for the data.
Conclusion: According to our model, most HIV transmissions among MSM in five US cities are from main sex partners. HIV prevention efforts should take into account the risks of HIV transmissions in male partnerships, and couples-based HIV prevention interventions for MSM should be given high priority in the US HIV prevention research portfolio.
Looking back at the people I have tested positive in my 5 years of HIV-testing, I have to say that the vast majority (probably 70% or more) had fewer than five sex partners in a year, with a mean around 2 or 3. I think there is a certain comfort level when you state that you are "monogamously oriented." Let's run down the thinking:
Person A meets Person B. Both have a series of long-term (defined as 6 months or longer) relationships in their history, possibly a handful of shorter relationships, and very few very short term (one night to one week) relationships. In total, we have two people whose lifetime number of sexual partners is less than 10, maybe 20 at the very outset. Compared to the stereotype of gay men, that is extremely low. If you add in the fact that perhaps one or both do not actively access the gay community and may not identify as "gay," you're talking about a smaller number and a decreased perception of risk.
So Person A and Person B enter into a relationship. Perhaps one (or both) have been recently tested, within the last 3 months, say. A few months in, they both feel comfortable with each other and they decide that because they perceive each other (and themselves) to be low risk that it would be OK to stop using a condom... or, perhaps, they were drunk or especially hot one night and just stopped.
But, let's say Person B became infected 3 months before the relationship began, or even as far as 9 months before the relationship began (HIV takes 3-6 months to show up on standard HIV-screening tests), perhaps with the last long-term relationship, or perhaps in a mistake one night with one of the other partners. But, because he was tested, he does not believe that he is still seroconverting and still an "invisible" positive. Person B becomes the insertive partner in intercourse, thus infecting Person A.
In no part of that scenario was a truly awful decision made; rather, I think it is an easy series of decisions to make in the context of a monogamous relationship. And, now, we have two HIV+ individuals who are unaware of their status. Then, they don't get tested because they are together. They break up a few months later, Person B, perhaps a year or more later, thinks about getting tested... and finds he is HIV+. He contacts Person A who got tested immediately after the relationship ended and found that he was as yet undetectable, and now Person A is in another relationship with Person C where a condom is not being used. Person A, maybe, is still within that 6 month window, tests again, receives a non-reactive/negative result (though he is actually infected) and the cycle goes on.
What's the proper course of action? Monogamy with a condom for six months or more, get tested together, and then have the condom discussion. Contact STOP AIDS (513-421-2437) to get your test done. It's only 20 minutes, and there's no blood.
It's worth your time.