Antiviral drug resistance

Antiviral drug resistance is the ability of a virus to reproduce despite exposure to a drug that previously inhibited it, usually because viral genetic changes reduce the drug’s effect.

Viral mutation: A change in the genetic material of a virus. Mutations can alter drug targets or viral functions, allowing replication during treatment.
Antiviral susceptibility testing: Laboratory testing that measures how strongly an antiviral drug inhibits a virus. It can reveal reduced drug activity in a patient’s viral sample.
HIV reverse-transcriptase inhibitor resistance: Reduced HIV susceptibility to drugs that inhibit reverse transcriptase. Resistance to early HIV drugs established a central example of treatment-driven viral evolution.
Antiviral treatment failure: The failure of an antiviral regimen to achieve or maintain its intended clinical or virologic effect. Failure can result from resistance, but also from adherence, dosing, or other factors.
Drug target: A molecule or biological process that a drug acts on to produce an effect. Changes in the viral target can weaken a drug’s binding or inhibition.
HIV drug resistance testing: Genetic or phenotypic testing used to identify HIV variants resistant to antiretroviral drugs. HIV resistance testing guides selection of an effective treatment regimen.
Oseltamivir resistance: Reduced influenza virus susceptibility to the neuraminidase inhibitor oseltamivir. Its emergence and spread show that resistance can matter at population scale.
Intrinsic antiviral resistance: A virus’s naturally low susceptibility to a drug, present without prior selection by that drug. Intrinsic resistance is baseline insensitivity, unlike resistance acquired during drug exposure.
Viral fitness: A virus’s capacity to survive and reproduce in a particular environment. Resistance mutations can enable treatment survival while reducing replication without the drug.
Hepatitis C resistance-associated substitution: A viral genetic change associated with reduced susceptibility to a hepatitis C drug. Such substitutions can affect response to direct-acting antiviral treatment.

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