Daniel Lee, M. D.Assistant Clinical Professor of Medicine
UCSD Medical Center
Owen Clinic
Important note: Information in this article was accurate in 2004. The state of the art may have changed since the publication date. Doc,
Several replies to questions mention that the risk of HIV
transmission from unprotected sex is roughly 1%? What is the
source of/support for this estimate? Does the 1% estimate
decrease significantly if the HIV+ partner's viral load is
suppressed to undetectable (<50/ml)? Does the risk of male to
female transmission differ from the risk of female to male
transmission?
Daniel Lee, M. D.
Assistant Clinical Professor of Medicine
UCSD Medical Center
Owen Clinic
I am not exactly sure where the source of this 1% estimate comes from, but I have included 2 references (see below) for you to review, if you are more interested. My suspicion is that the 1% estimate that you quote is decreased (as to how much - not sure) if your HIV+ partner's viral load is suppressed. However, there is not great correlation between one's viral load in the blood and one's viral load in the semen. Generally, it is accepted that if one's viral load is low in the blood, it is likely lower in the semen than if that same person's viral load was higher (see 2nd reference). But, we do not necessarily know if the viral load in the semen is undetectable or not - which is the real question. In regards to transmission from male to female or female to male, I honestly do not know if studies have actually looked at this question. Hope this helps. Thanks for your question.
The 2 references are:
1. Varghese, B et al. Reducing the Risk of Sexual HIV Transmission. Sex Transm Dis. 2002 Jan;29(1):38-43
2. Incorporating HIV Prevention into the Medical Care of Persons Living with HIV. MMWR Jul 18, 2003 / 52(RR12);1-24
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