The Study

(H1N1) 2009 viruses in the United States were oseltamivir resistant, compared with 0.5 % during the 2009–10 infl uenza season. Of resistant viruses from 2010–11 and 2009–10, 26 % and 89%, respectively, were from persons exposed to oseltamivir before specimen collection. Findings suggest limited community transmission of oseltamivir-resistant virus. During the 2009–2010 infl uenza pandemic, when pandemic (H1N1) 2009 virus was the predominant circulating infl uenza virus (1), the prevalence of oseltamivir-resistant pandemic (H1N1) 2009 viruses in the United States was 0.5%. Of the patients with oseltamivir-resistant virus infection, 89 % had been exposed to oseltamivir before specimen collection (2). We describe patients with oseltamivir-resistant pandemic (H1N1) 2009 virus infections during the 2010–11 infl uenza season