Sixty-two severe and critical patients with 2009 influenza A （H1N1） in Shanghai, China

Background Pandemic influenza A （H1N1） emerged rapidly in China in May 2009. Preliminary comparisons with seasonal influenza suggest that pandemic 2009 influenza A （HIN1） disproportionately affects younger ages and causes generally mild disease. To characterize disease progress, comorbidities, and treatment outcomes among consecutive severe and critically ill patients in a hospital served as a reference center for the care of patients with HIN1 in Shanghai, China.Methods A retrospective study on 62 severe and critically ill patients with 2009 influenza A （H1N1） was conducted in Shanghai Public Health Clinical Center. Demographic data, symptoms, comorbidities, disease progression, treatments, and clinical outcomes were collected for analysis.