Amantadine resistance in relation to the evolution of influenza A(H3N2) viruses in Iran

The aminoadamantanes, amantadine and rimantadine, have been used to prevent and treat influenza A virus infections for many years. Several reports have shown an increased level of resistance to these drugs, particularly among influenza A(H3N2) subtype viruses, during recent years. We observed an increase in amantadine resistance, due to a Ser31Asn mutation in the M2 channel protein, among A(H3N2) viruses circulating in Iran during 2005–2007. Sequence analyses of the haemagglutinin and neuraminidase genes as well as the M gene of these viruses revealed that the emergence of resistance was in general consistent with the progressive worldwide evolution of H3N2 viruses.