Morbidity and Mortality Associated With Nosocomial Transmission of Oseltamivir- Resistant Influenza A(H1N1) Virus

Abstract
A global emergence and rapid spread of oseltamivir-resistant influenza A(H1N1) viruses carrying a neuraminidase (NA) gene with an H274Y (N2 numbering; H275Y in N1 numbering) amino acid substitution has been observed since January 2008.1-3 Viruses carrying this mutation are presumed to exhibit attenuated pathogenicity,4 compromised transmission,5 and reduced lethality.6 However, current widespread circulation of oseltamivir-resistant influenza A(H1N1) viruses associated with typical influenza illnesses and viral pneumonia suggest that these viruses retain significant transmissibility and pathogenicity.2,3,7,8 While these resistant variants may cause significant mortality and retain efficient transmission, these properties have not yet been firmly established.