Emergence of an Oseltamivir-Resistant Influenza A/H3N2 Virus in an Elderly Patient Receiving a Suboptimal Dose of Antiviral Prophylaxis

We report the emergence of an influenza virus A/H3N2-E119V neuraminidase variant from an elderly patient with renal dysfunction who received a suboptimal dose of oseltamivir prophylaxis. In neuraminidase inhibition assays, the E119V variant showed a 413-fold increase in the 50% inhibitory oseltamivir concentration and grew at titers comparable to those of the wild type in vitro.