Emergence of multidrug resistant influenza A(H1N1)pdm09 virus variants in an immunocompromised child treated with oseltamivir and zanamivir.

Prolonged treatment of an immunocompromised child with oseltamivir and zanamivir for A(H1N1)pdm09 virus infection led to the emergence of viruses carrying H275Y and/or E119G in the neuraminidase. When phenotypically evaluated by neuraminidase inhibition, the dual H275Y-E119G substitution caused highly reduced inhibition by four neuraminidase inhibitors including oseltamivir, zanamivir, peramivir and laninamivir