Analysis of sentinel surveillance results of influenza in Huzhou, 2006-2007

Objective　To determine the epidemiological features of influenza and the virus variation in Huzhou. Methods　Surveillance data, virus isolation and identification results and outbreak information of influenza-like illnesses (ILI) in Huzhou from 2006 to 2007 were collected for analysis. Results　A total of 36 849 ILI cases were reported by surveillance hospitals from 2006 to 2007, accounting for 5.57% of the total outpatients. Most cases were children aged＜14 years, accounting for 80.48% of the total cases. The incidence peaked during March-April and during July -August, 2006, respectively, while in 2007 the influenza activity was stable without obvious seasonality. A total of 47 strains of influenza virus (H3N2, H1N1 and B) were isolated in 2006 and 2007 with the positive rate of 9.51%. Eleven outbreaks caused by B virus occurred in middle and primary schools. Conclusion　The incidence might peak in spring and summer and different strains might be predominant in a year in Huzhou. The sensitivity of the influenza surveillance network should be further improved.