Epidemiological analysis for influenza surveillance in Pudong New Area from 2008 to 2010

Objective To explore influenza trend and its strains of the virus in Pudong New Area.Methods Epidemiological surveillance:Cases of influenza-like illnesses (ILI) were filled in forms weekly by monitoring hospitals and submitted to the network. Etiological surveillance:5~20 mouth-rinsing samples were collected and detected for influenza virus weekly by monitoring hospitals and then submitted to Disease Control and Prevention Center of Pudong New Area for pathogen detection of influenza.Results Epidemiological and pathogenic surveillance indicated that ILI percentage and positive rate of influenza virus were at the peak in March and August 2008,and March,August and December 2009 and September 2010.The predominant epidemic strain was Influenza B(Yamagata) in February 2008,A(H₃N₂) in March 2008,A(H₁N₁) from July 2008 to February 2009,A(H₃N₂) from July to August 2009,swine A(H₁N₁) from September 2009 to January 2010,B (Victoria) from February to March 2010 and A(H₃N₂) from August to Eleven 2010.Conclusion Two peaks were observed in 2008:one in winter-spring,and the other in summer-autumn.Three peaks were observed in 2009:one in the beginning of 2009,another in summer-autumn and the last in the end of 2009.Summer-autumn peak was observed in 2010.Influenza virus subtypes were prevalent in circulation.