Epidemiological features of pandemic influenza A(H1N1) in Beijing,2009

Objective To describe epidemiological features of pandemic influenza A(H1N1) cases in Beijing,2009.Methods The data of reported pandemic influenza A(H1N1) cases in Beijing were collected and analyzed for their epidemiological features with SPSS software.Results A total of 10 802cases of influenza A(H1N1) were confirmed in 2009,including 621 severe and critical cases and 73 deaths with a case-fatality rate of 0.7 percent.Based on the incidence dates of the cases,the pandemic could be divided into four phases,i.e.,imported from abroad,local transmission,local spread,stable and decreasing phase.There were 52.2 percent of the cases were students at high school,and 15.9 percent of severe case and 23.3 percent of critical case were retirees,respectively,with a male to female ratio of 1.3:1.The highest incidence was reported in Huairou district.Conclusion Epidemic of influenza A(H1N1) in Beijing reached the peak in October 2009,with most of infected cases in students and young people.Most of the severe and critical cases and deaths are retirees.