Prevalence of Oseltamivir-Resistant 2009 H1N1 Influenza Virus among Patients with Pandemic 2009 H1N1 Influenza infection in NRITLD, Tehran, Iran

Background: 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. Materials and Methods: 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. Results: 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. Conclusion: 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.