Epidemiological and clinical characteristics of confirmed cases of 2009 pandemic influenza A(H1N1) in Jinhua, Zhejiang province, 2009-2010

Objective To analyze the epidemiological and clinical characteristics of confirmed cases of 2009 pandemic influenza A (H1N1) in Jinhua during 2009-2010, and provide evidence for the prevention and control of the disease. Methods The data of surveillance and investigation of 2009 pandemic influenza A (H1N1) virus infection in JInhua during this period were collected to conduct descriptive epidemiological analysis on its time, regional and population distributions, and severe cases chronic medical condition, complication and outcome. Results A total of 687 confirmed cases of 2009 pandemic influenza A (H1N1) were reported with the incidence of 13.5/lakh, 108 were severe cases and 6 were fatal, accounting for 15.7% and 0.9% respectively. Most cases occurred in developed area or area with frequent population floating. The populations affected mostly were children, adolescents and students. The incidence of severe cases differed in different age group(2=7.718,df=2,P＜0.05), and 31 (28.7%) cases were with chronic medical conditions. Patients with chronic medical conditions were more likely to become severe cases (2=6.651,P＜0.05). Pneumonia, respiratory failure and acute respiratory distress syndrome (ARDS) were the main complications. Conclusion The infection of 2009 pandemic influenza A (H1N1) virus was generally mild in Jinhua, which affected children and adolescents mostly. Clinical severity of the infection differed in different age group. Chronic medical condition was one of risk factors of severe cases. Pneumonia, respiratory failure and ARDS were the main complications.