Case report of sexual transmission when viral load suppressed to <50 copies/mL

Simon Collins, HIV i-Base

A case report published in Antiviral Therapy in Sepetember is important to inform the discussion on risk of sexual transmission by patients meeting the factors outlined in the Swiss Statement earlier this year (durable viral suppression to <50 copies/mL for >6 months, perfect adherence, no STIs).

Martin Stürmer from the Goethe University Hospital, Frankfurt, and colleagues described the case of a monogamous gay couple where the HIV-negative partner became infected. The HIV-positive partner, diagnosed in January 1999, started AZT/3TC/efavirenz in July 2000, achieving undetectable viral load within four months that was maintained for the next four years.

The man’s partner tested HIV-negative in June 2002 but HIV-positive in July 2004. The couple did not have other partners, but reported having unprotected sex from May 2003.

Phylogenetic analysis showed close relationship between the two viruses and ruled out the source of infection being a third party. Throughout the period, the HIV-positive partner reported good adherence, with no STIs, confirmed by his medical records.

The authors concluded “this should be added to the discussion of prevention strategies, which should not advise the abandonment of safer-sex practices without referring to the relatively low but not impossible risk of HIV-1 transmission in this context”.


Accurate, verified cases are important because of the lack of post-HAART data on transmission. No one is looking at it and no one is reporting it. One criticism of the Australian paper in the Lancet that modelled population risk from stopping condom use by assuming a linear relationship between viral load and risk, was that there maybe a cut-off level below which no transmission occurs. This case shows that criticism may not be valid for anal sex. We now need to know if there are similar cases for vaginal sex transmission?

Prevention risks are individual. An acceptable risk for one person is unacceptable for another. Without this case everything is theoretical.

With it, you can say that the risk is likely to be real for anal sex.

The report raises two issues for which we need more information: anal sex (most modelling is based on vaginal sex) and viral load in semen (the report below from the sperm-washing service in Paris highlighted 5% discordance between blood and semen).

The conclusions from this case report are different, based on each of the practical example used for the context of the Swiss statement.

Firstly, if trying for a baby, it is important to have semen viral load checked. Secondly, that risks are still very low for serodifferent couples, for example in cases of a single condom break, but not low enough to stop using condoms routinely.


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

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