How much does viral load need to fall to halve HIV transmission risk?

The partners in Prevention study of acyclovir as an HIV prevention measure showed that an average viral load reduction of .74 log is needed in order to reduce the risk of HIV transmission by 50%. The has important implications for future studies of HIV treatment as prevention.

This study though scant in data really hits the nail on the head. Microbicides, barrier protection for women, pre-exposure prophylaxis with antiretroviral drugs for those having unprotected sex have by and large failed as a preventative measure. Condoms and circumcision although successful are not particularly appealing to men having sex. HIV treatment as Prevention is the best way we believe of preventing the spread of HIV, especially in resource poor countries. In fact mathematical models in some provinces in Africa have shown that treating everyone could come close to stopping the spread of the infection in approximately 7/1/2 years. With no HIV preventative vaccine in sight, treatment as prevention may be the way to go.