Prevalence of oseltamivir-resistant 2009 H1N1 influenza virus among patients with pandemic 2009 H1N1 influenza infection in NRITLD, Tehran, Iran

Oseltamivir-resistant cases were reported during the 2009 pandemic influenza outbreak and therefore, widespread emergence of oseltamivir-resistant 2009 H1N1 virus is imaginable. Underlying medical conditions like immunosuppression increase the chance of oseltamivir resistance. In a retrospective cross-sectional study, respiratory tract specimens of confirmed cases of 2009 H1N1 influenza referred to the Masih Daneshvari Hospital were analyzed for presence of H275Y mutation. From November 2009 through March 2010, oseltamivir-resistant 2009 H1N1 infection was observed and confirmed in 4 patients [including 2 immunocompromised patients] by performing H275Y mutation molecular testing. Close monitoring of resistance to neuraminidase inhibitors is essential in tertiary care centers. The H275Y mutation [oseltamivir-resistant genotype] could appear in the absence or presence of selective drug pressure