Background: Influenza viruses are one of the most important etiological agents of res-piratory disease in humans and cause epidemics and pandemics with substantial mor-bidity and mortality worldwide. Vaccination and antiviral treatments are the sole and essential way for the prevention and control of influenza infection. During an influenza epidemic before the production of effective vaccine, antiviral treatments are the first step for the prevention and treatment of influenza infection. Adamantanes and neuraminidase inhibitors are influenza antiviral drugs. Because of the increase of drug resistant viruses, the aim of this study was the evaluation of the antiviral drug resistance in influenza A/H3N2 viruses from 2005-2013 in Iran. Methods: In this study 50 influenza A/H3N2 viruses isolated in cell culture were tested. All samples were subjected to M and NA gene sequencing at the National Influenza Center, School of Public Health, Tehran University of Medical Sciences. RNA was ex-tracted from 200 µl of cell culture supernatants using the Roche high pure viral nucleic acid kit. RT-PCR with the Qiagen one step RT-PCR kit was done. The expected size of the PCR products were analyzed by electrophoresis using 1% agarose gels. The PCR products were sequenced for finding the drug resistant mutants. Results: All influenza A/H3N2 viruses except four viruses circulating during 2005-2006 had Ser31Asn mutation at M2 channel protein. In the analysis of neuraminidase gene none of the A/H3N2 viruses had K292R, E119V and N294S mutations responsible for drug resistant strains. Conclusion: This study showed circulating A/H3N2 viruses was resistant to adaman-tanes but susceptible to neuraminidase inhibitors. The national data analyzed in this re-search may help increase knowledge about influenza virus antiviral drug resistance, which is a global public health concern. The authors suggested continuing this study and also the investigation of antiviral drug resistance of influenza A/H1N1 and B viruses.

Keywords: drug resistance, H3N2 subtype, influenza A virus

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