HIV transmission and antiretroviral therapy
Antiretroviral treatment greatly reduces the risk of transmitting HIV. Several very large studies have now shown that people with undetectable viral load do not pass on HIV to their sexual partners. However, there is still a possibility that HIV might be passed on during the period between starting treatment and viral load becoming detectable, which may take up to six months, or if viral load rebounds due to treatment failure.
A review of a large PrEP study conducted in couples where one partner had HIV and the other did not, has shown that when the partners with HIV became eligible to start antiretroviral treatment for their own health, there was still a risk that HIV could be passed on before they reached an undetectable viral load.