Purpose of review: The proportion of patients showing primary infection with HIV-1 that are already resistant to antiviral drugs has been steadily increasing. Such resistance is known to compromise therapy response. Most patients, however, are not diagnosed during their incident infection and, until recently, it was not known for how long resistant virus can be detected following infection. This article reviews reports on the stability of transmitted resistance in the absence of therapy.
Recent findings: It has now been shown that many resistance-associated mutations can persist for a considerable time following transmission in the absence of treatment and that such resistance can be further transmitted.
Summary: Since transmitted resistance can be detected years after infection, it is now worthwhile carrying out resistance tests on newly diagnosed patients in which it is known that the level of transmitted resistance in the population warrants such testing.