Drug | Virus | IC_{50} (nM) per season | Total IC_{50} (nM)^{a} | P value^{b} | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

2004-2005 | 2005-2006 | 2006-2007 | ||||||||||

Range (n) | Mean ± SD | Range (n) | Mean ± SD | Range (n) | Mean ± SD | Range (n) | Mean ± SD | Cutoff | Statistical cutoff | |||

Oseltamivir | A(H1N1) | 0.35-6.05 (53) | 0.96 ± 0.97 | 0.19-10.00 (258) | 1.15 ± 1.01 | 0.16-4.51 (817) | 0.84 ± 0.45 | 0.16-10.00 (1,128) | 0.91 ± 0.66 | 2.89 | 2.43 | <0.0001 |

A(H3N2) | 0.11-3.45 (142) | 0.52 ± 0.34 | 0.08-3.05 (186) | 0.59 ± 0.46 | 0.04-5.16 (908) | 0.40 ± 0.32 | 0.04-5.16 (1,236) | 0.44 ± 0.35 | 1.50 | 1.51 | <0.0001 | |

B | 1.24-11.63 (175) | 3.23 ± 1.63 | 0.70-7.95 (203) | 3.45 ± 1.36 | 0.19-10.48 (511) | 3.47 ± 1.24 | 0.19-11.63 (889) | 3.42 ± 1.35 | 7.47 | 8.64 | 0.122 | |

Zanamivir | A(H1N1) | 0.50-6.48 (53) | 1.12 ± 0.88 | 0.20-13.50 (259) | 1.30 ± 1.34 | 0.06-11.60 (822) | 0.98 ± 0.74 | 0.06-13.50 (1,134) | 1.06 ± 0.93 | 3.85 | 3.32 | <0.0001 |

A(H3N2) | 0.49-13.98 (140) | 3.66 ± 2.51 | 0.14-11.77 (186) | 2.62 ± 2.04 | 0.15-20.00 (907) | 2.35 ± 2.16 | 0.14-20.00 (1,233) | 2.54 ± 2.22 | 9.20 | 9.93 | <0.0001 | |

B | 1.12-16.51 (175) | 4.21 ± 2.65 | 0.85-17.86 (203) | 4.84 ± 2.77 | 0.35-12.00 (511) | 3.36 ± 2.14 | 0.35-17.86 (889) | 3.87 ± 2.47 | 11.29 | 14.21 | <0.0001 |

↵

*a*A total of 3,261 isolates were tested(12 extreme outliers were excluded from the statistical analysis for the respective drug eliciting the outlier IC_{50}s). The cutoff value was determined based on the elected criterion of the mean IC_{50}value + 3 standard deviations (SD). The statistical cutoff value was determined based on the IC_{50}value of >*X*_{0.75}+ 3 IQR.↵

*b**P*value was determined by analysis of variance (where α = 0.05).