oseltamivirresistant

Oseltamivirresistant refers to influenza viruses that exhibit reduced susceptibility to oseltamivir, a neuraminidase inhibitor used to treat and prevent influenza A and B infections. Resistance primarily results from mutations in the neuraminidase NA gene, which alter the drug-binding site and diminish the drug’s ability to inhibit the enzyme. In some viruses, resistance may be accompanied by changes in viral fitness or transmissibility, and compensatory mutations can influence these effects.

Specific mutations have been linked to oseltamivir resistance. The best known is H275Y in the neuraminidase of certain A(H1N1) viruses, but other substitutions such as E119V, R292K, and N294S have been associated with reduced oseltamivir susceptibility in various subtypes. Resistance can arise spontaneously or during antiviral therapy, particularly in immunocompromised individuals or when treatment adherence is suboptimal. Resistant viruses can spread under some circumstances, though transmission may depend on the resulting fitness of the virus.

Diagnosis relies on phenotypic assays that measure drug inhibition of neuraminidase or genotypic tests that identify known resistance mutations. In cases of oseltamivir resistance, alternative antiviral options such as zanamivir—often active against resistant strains—and, in appropriate circumstances, peramivir, may be used. Treatment decisions consider patient age, comorbidities, infection severity, and access to susceptibility information.

Public health surveillance by organizations such as the WHO and national health agencies monitors oseltamivir resistance trends to guide antiviral use and vaccination strategies. The phenomenon underscores the importance of antiviral stewardship, vaccination, and ongoing research to maintain effective influenza management.