Efficient control of pandemic 2009 H1N1 virus infection with intravenous zanamivir despite the lack of immune function.

A teenager who acquired 2009 H1N1 influenza A lower respiratory tract infection during total bone marrow and lymphoid aplasia, in the setting of human leukocyte antigen-haploidentical hematopoietic stem cell transplantation, was successfully treated with intravenous zanamivir. This case demonstrates efficient control of pandemic influenza infection by intravenous zanamivir in the absence of any functional immune system, thus suggesting profound antiviral activity.