Emergence of a Multidrug-Resistant Pandemic Influenza A (H1N1) Virus

To the Editor: Since the outbreak of influenza A (H1N1) virus pandemic, almost 300 cases of infection with an oseltamivir-resistant influenza virus have been reported to the World Health Organization as of June 2010.1 These strains typically contain a single histidine-to-tyrosine substitution at position 275 (H275Y) of the viral neuraminidase, but they remain susceptible to zanamivir. Successful clearance of an oseltamivir-resistant virus with zanamivir, the other approved neuraminidase inhibitor, has been reported.2 We report the emergence of a pandemic influenza virus in a patient treated with neuraminidase inhibitors, with a novel resistance pattern that conferred resistance to oseltamivir, zanamivir, and . . .