Up to 76 H1N1 outpatients and inpatients were chosen from August to December 2009 in the Department of Infectious Diseases, First Affiliated Hospital, School of Medicine, Zhejiang University. Among these, 36 cases were severe and 40 cases were moderate (Table 1 ). In addition, 20 healthy volunteers who were not infected with 2009 H1N1 virus, were selected as controls. There were no statistical differences between their ages and genders compared with the H1N1 patients.