HIV transmission and primary drug resistance.

Transmission of HIV viruses harboring resistance mutations is already a major concern in developed countries, with the potential to impact on therapeutic strategies. Several factors influence the transmission of such viruses, including viral replication fitness and transmission fitness, although behavioral characteristics must also be considered. Rates of transmission of specific mutations are related to therapeutic strategies. Reports of the transmission of multidrug-resistant viruses should alarm the medical community. An additional concern is the use of monotherapy with nevirapine for the prevention of mother-to-child transmission of HIV in developing countries as this practice selects for resistance to nonnucleoside reverse transcription inhibitors and could limit future therapeutic options of both the mothers and infected children. HIV treatment guidelines have evolved, shifting from more aggressive to more conservative approaches. This change of strategy has had a direct impact on the prevalence of drug-resistant virus in the population and the transmission of resistant viral species.