I am a bisexual man in my late 30s, in a heterosexual relationship. A few days ago I cheated on my partner. I met 50 year old married man online. We engaged in oral sex. Rather unexpectedly he ejaculated in my mouth. This was about one hour after I brushed my teeth. I spat out the semen right away and gargled my mouth with mouth wash. I asked him if he had any diseases (specifically, if he was 'clean' - not a nice term to use I know). He said that he is sure that he is. However, he then added that he actually never got tested ! He just assumed that he was because he only just broke off a long term affair with another male, who tested regularly and was negative, rarely meets anyone else and 'chooses carefully what he does and who he does it with' (what ever that means !)

This freaked me out a little and now I am worried. The guilt certainly does not help. I am worried most about HIV infection, particularly passing on to my partner. Everywhere I read it says the risk are small. I've read in some websites where it says that it is so small that testing is not required. I don't know what I should do ! Should I stop worrying? In the mean time I plan to use condoms the next time I have sex with my partner.

All things considered, you are at little or no risk for HIV or other STDs from this event -- to an extent that you can safely continue your normal sexual practices with your regular partner and don't need testing except maybe for reassurance. Here's why:

Although gay men have higher rates of STD than most heterosexuals, your partner probably is indeed at low risk for all STDs, both on the basis of his sexual history and his age. Statistically, the rates of all STDs are much lower at age 50 than, say, 20-30.

Second, oral sex can be considered safe sex in regard HIV and all STDs -- low risk for all infections and zero for some. To focus on HIV, for example, one analysis is that if the penile partner is infected, the average transmission risk to an oral partner by fellatio is around once for every 10,000 exposures. That's equivalent to giving BJs to infected men once daily for 27 years before transmission might be likely. And these figures assume ejaculation in the mouth. Actually, the effect of ejaculation isn't known, but in general it is not believed to signficantly elevate the risk of any STD compared to fellatio without ejaculation.

Since your main concern is HIV, the most reassuring thing you can do quickly is to contact your male partner and ask him to be HIV tested at this time. Even though it seems he is low risk, it is frankly irresponsible for him to have not been tested for HIV before now. All people, regardless of sexual risk, should be tested for HIV at least once. Tell him he would be doing you a great favor. While he's at it, he could also have a syphilis blood test and a urine test for gonorrhea and chlamydia. The expected negative results would prove you're home free in regard to the tested infections.

If your partner doesn't go along or you choose not to go that route, for reassurance you could be tested for HIV. A 4th generation (antigen-antibody, "duo") blood test would be conclusive at 4 weeks. However, I stress all this is purely for reasrruance. Simply on the basis of statistical probability, the chance you caught HIV is sufficiently low that there is really no medical need, and if somehow I were in your situation, I probably would not do it and would continue unprotected sex with my wife. But I'm not you, and you'll have to make your own decision about testing and perhaps condoms or abstinence with your partner.

I hope this has been helpful. Best wishes--  HHH, MD

Thanks for your prompt reply.

I find your reassurances...reassuring ! :-)

I guess the odds of 1 in 10,000 is strongly in my favour. If you factor in the prevalence of HIV amongst gay men in Australia ( about 11% - pretty high isn't it?), the probability of getting infected is about 1 in 100,000 (forgive me if my mathematics or reasoning is flawed!)

I spoke to my 'friend' about getting tested but he seems pretty confident that he is free of any diseases (confidence that could possibly be misplaced). But I do understand that with most partnered bisexual men who has issues with infidelity,  going for a 'blood test' out of the blue would raise suspicion with their partners.  I guess for some, ignorance is bliss.

But anyway, I feel reassured enough to forgo testing. Your explanation is also probably consistent with my personal experience - I've never met anyone claims to have been  infected through giving a BJ (Though I meet a fraction of what you see in your work obviously)

Again, many thanks for your reply

Now knowing where you are, I'll comment that Australia's sexual health centres comprise the world's very best network of STD/HIV clinics. If you change your mind about testing, you'll never go wrong visiting your local SHC, especially if you're in a major urban area. The Sydney and Melbourne clinics are the best of the best. (I'm personally closed to many in the leadership of both.) (This isn't intended to imply you need test, only recognizing that many in such circumstances nevertheless decide to do it for additional reassurance.)