• Weijuan Huang, Minju Tan, Xiang Zhao, Yanhui Cheng, Xiyan Li, Junfeng Guo, Hejiang Wei, Ning Xiao, Zhao Wang, Dayan Wang, and Yuelong Shu.
• Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Key Laboratory for Medical Virology, National Health, Beijing102206, China.
• Zhonghua Yu Fang Yi Xue Za Zhi. 2015 Jun 1; 49 (6): 481-4.

ObjectiveTo analyze the susceptibility of influenza A (H3N2) viruses to neuraminidase inhibitors during 2011-2012 in Mainland China.MethodsAll the tested viruses were obtained from the Chinese National Influenza Surveillance Network, which covers 31 provinces in mainland China, including 408 network laboratories and 554 sentinel hospitals. In total 1 903 viruses were selected with isolation date from January 1, 2011 to December 31, 2012 in Mainland China, among these viruses, 721 were confirmed to be influenza A (H3N2) virus by Chinese National Influenza Center and tested for the susceptibility to oseltamivir and zanamivir using chemiluminescence-based assay. The neuraminidase inhibitor sensitive reference virus A/Washington/01/2007 (119E) and oseltamivir resistant virus A/Texas/12/2007 (E119V) were used as control in this study. The t -test was used to compare the difference of NAI susceptibility of viruses isolated from different years.ResultsThe half maximal inhibitory concentration (IC₅₀) of A/Washington/01/2007 for oseltamivir and zanamivir was (0.10 ± 0.02) and (0.30 ± 0.05) nmol/L, respectively. The IC₅₀ of A/Texas/12/2007 for oseltamivir and zanamivir was (4.27 ± 1.60) and (0.20 ± 0.03) nmol/L, respectively. Among the 721 influenza A (H3N2) viruses, 132 influenza A (H3N2) viruses were isolated in 2011 and 589 influenza A (H3N2) viruses were isolated in 2012. The IC50 for oseltamivir ranged from 0.04 to 0.62 nmol/L for viruses isolated in 2011 and ranged from 0.02 to 0.95 nmol/L for viruses in 2012, and the IC₅₀ of all the viruses tested was within 10-fold IC₅₀ (1.0 nmol/L) of the neuraminidase inhibitor sensitive reference virus A/Washington/01/2007. The IC50 of zanamivir ranged from 0.12 to 0.80 nmol/L for viruses in 2011 and ranged from 0.04 to 0.72 nmol/L for viruses in 2012, and was within 10-fold IC₅₀ (3.0 nmol/L) of the neuraminidase inhibitor sensitive reference virus A/Washington/01/2007.ConclusionThe influenza A(H3N2) viruses isolated during 2011-2012 in Mainland China were tested to be sensitive to oseltamivir and zanamivir.

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