Antiretrovirals, Viral Load, and HIV Transmission

On January 30, 2008, the Swiss AIDS Federation released a report which indicated that HIV-positive people who are taking antiretroviral drugs cannot transmit the virus during sex provided a) they have adhered to their treatment regimes and have had suppressed HIV viral loads for at least six months and b) are otherwise free of sexually transmitted infections. (Note that the report is in French; click here for an unofficial English translation.)

While this is promising news, the AIDS Committee of Toronto (ACT) urges that the announcement should be met with caution for a number of reasons:

1. The studies, which took place in Spain and Brazil over the past decade, focused on vaginal intercourse between serodiscordant1, presumably monogamous heterosexual couples. The findings of the studies do not account for the risk of transmission through anal sex. The level of risk associated with anal sex between an HIV-positive person with undetectable viral loads and an HIV-negative partner remains unclear.

2. Approximately 10-15%2 of men and 25%3 of women who adhere to antiretroviral treatments and have undetectable viral loads in their blood continue to have detectable amounts of the HIV virus in their semen/vaginal secretions and are at risk of transmitting the HIV virus during condomless sex.

3. No one can be certain of their own or their sexual partner’s viral load at all times. There is always a level of risk associated with condomless sex.

ACT stresses that all people should continue to practice safer sex, including those who are in a serodiscordant relationship or have multiple sexual partners.


Other Responses to the Report:



1 i.e. one partner is HIV-positive, the other is HIV-negative.
2 Leurez-Ville et al AIDS, 2002 and Barroso et al JAIDS, 2003
3 Fiore et al AIDS 2003