US Patent 8465960 Influenza B viruses with reduced sensitivity to neuraminidase inhibitors

An isolated influenza B virus which has reduced sensitivity to one or more neuraminidase (NA) inhibitors, wherein the reduced sensitivity to one or more NA inhibitors is associated with a residue in NA other than Ile at position 222, a residue in NA other than Ser at a position 250, or a residue in NA other than Gly at position 402, as well as methods to detect such a virus or determine agents that inhibit the infection or replication of such as virus, are provided.