Emergence and control of resistance to antiviral drugs in resistance in herpes viruses, hepatitis B virus, and HIV.

: This article describes the biology of antiviral drug resistance with regard to herpes viruses, hepatitis B virus, and HIV. The emergence of antiviral drug resistance is testimony to the potency of current antiviral drugs. Natural selection of such viral variants occurs, such that the strains that are 'fittest' in the presence of the drug persist. Phenotypic and genotypic assays are now available to test clinical viral isolates for resistance. At present, the clearest indication for such testing is in aciclovir-resistant herpes simplex infection. It is important that other resistance assays are subject to studies of clinical utility before their widespread use.