Hemagglutinin (HA1) mutations specific to isolates with reduced zanamivir sensitivity.

Each 2009 isolate was sequenced directly following three passages in MDCK cells, without plaque purification. Sequence heterogeneities were observed at some locations and alternate amino acids at such locations are shown in the table. Amino acids different from reference strains are noted in bold. Sequence data noted with H3 numbering scheme, as previously described [42].