Comparisons of oseltamivir‐resistant (H275Y) and concurrent oseltamivir‐susceptible seasonal influenza A(H1N1) virus infections in hospitalized adults, 2008–2009

In an observational cohort study, we found that adults hospitalized for oseltamivir‐resistant (H275Y) seasonal H1N1 influenza (n = 46) were older than those infected with oseltamivir‐susceptible strains (n = 31) [74(IQR 59–83) versus 64(IQR 48–76) years; P = 0·045], and most had major comorbidities (78% versus 65%). Disease severity and clinical outcomes were comparable between the two groups: radiographic pneumonia 40–42%, supplemental oxygen use 47–48%, critical illness 11–13%, median duration of hospitalization 5–6 days, death rate 6–9%. Failure to receive effective antiviral therapy was associated with progression to critical illness (23% versus 0%, P = 0·016) and death (20% versus 0%, P = 0·033) in hospitalized patients with seasonal H1N1 influenza.