Question

How high is the risk of transmission between two men when on treatment?

2 May 2012. Related: All topics, HIV transmission, Sero different couples.

I was wondering whether you could give me some advice re. infection between a male couple of different HIV status.

I have been HIV positive for 4 years and started treatment 6 months ago, Atripla. I am currently undetectable and CD4 of c 800. My partner is HIV negative and circumcised no known STDs. It has been quite challenging to practice safer sex 100% of the time and I am concerned that even though my labs are exceptionally good there could still be a risk of infection.

I am aware that there is a study suggesting that successful treatment reduces the risk of infection by 96% but I wonder whether that study also applies to homosexual couples.

I would appreciate if you could put me in the right direction to find some information bearing in mind that I am aware I-base does not answer questions regarding infection any longer. Many thanks.

Answer

Answer: Rebecca McDowall

The question of whether or not treatment provides the same protection to gay couples as to heterosexual couples has not yet been answered. While the protective measure of treatment is the same the mechanics of anal sex mean that it is a higher risk activity than vaginal sex. This is regardless of whether anal sex is between a man and woman or two men. The HPTN 052 study that you mentioned- which showed the 96% drop in risk- was modeled on couples only having vaginal sex.

The reason why anal sex is higher risk is due to the lesser protective value of the rectum compared to the vagina. This link has more information about skin, mucous membranes and HIV transmission.

The partner study that is currently underway is looking at the risk of sexual transmission between sero-discordant couples- where one partner is positive and the other negative. It is hoped that this study will help to answer questions like yours.

The following links are to studies looking at the risk of sexual transmission in homosexual men. The links have been taken from our guide to HIV testing and risks of sexual transmission.

STUDIES ON RISK OF SEXUAL TRANSMISSION IN MEN WHO HAVE SEX WITH MEN

Jin F et al. Per-contact probability of HIV transmission in homosexual men in Sydney in the era of HAART. AIDS 2010, 24(6): 907–91.

Baggaley RF et al. Infectiousness of HIV-infected homosexual men in the era of highly active antiretroviral therapy. AIDS 2010. 24(15): 2418-20.

Hallett TB et al. Estimating the risk of HIV transmission from homosexual men receiving treatment to their HIV-uninfected partners. Sexually Transmitted Infections. 2011; 87(1):17-21.

Wilson DP et al. Infectiousness of HIV-infected men who have sex with men in the era of highly active antiretroviral therapy. AIDS 2010. 24; 24(15): 2420-1.

Stürmer M et al. Is transmission of HIV-1 in non-viraemic serodiscordant couples possible? Antivir Ther. 2008;13:729-732.