Oseltamivir-resistant influenza A(H1N1) 2009 virus in Greece during the post-pandemic 2010-2011 season

Information on the drug susceptibility of influenza epidemic strains is important for antiviral resistance monitoring. In Greece, the 2009-2010 pandemic waves were very mild and seroprevalence rates remained low after this influenza season, resulting in exclusive detection of the pandemic strain during the 2010-2011 influenza season. In the present study during the post-pandemic 2010-2011 season, 50 consecutive influenza A(H1N1) 2009 virus-positive samples from patients hospitalised in Greek hospitals were analysed for resistance to the neuraminidase inhibitor oseltamivir. All patients were hospitalised with severe influenza complications and had previously received oseltamivir. Influenza A(H1N1) 2009 virus detection and testing for oseltamivir resistance were performed with real-time PCR amplification assays. The H275Y substitution associated with resistance to oseltamivir was identified in two immunocompetent patients who received oseltamivir treatment for 3 days and 5 days, respectively. In both cases, patients were discharged in good condition despite development of resistance to antiviral treatment.