Features of outbreak of influenza-like infection in 2009 in Jining.

Aim To understand the features of outbreaks of influenza-like illness(ILI) in Jining,and provide evidence for scientific prevention and control of the disease.Methods Restrospective analysis of data of outbreaks of ILI in Jining was performed.Results There 22 outbreaks of ILI were reported,cumulative numbers of ILI were 554,with an incidence of 1.67%.18 cases(81.82%) of the ILI occurred from September to December;21cases(95.45%) occurred in primary schools and middle schools;There 81.82% outbreak were due to influenza A virus infection.All positive samples detected by PCR were immediately inoculated with MDCK cells for virus isolation and culture and 15 strains were isolated from 5 cases including one subtype H3N2 and fourinfluenza A virus subtype H1N1.The infections Increased significantly since the beginning of September and mainly concentrated in autumn and winter.Conclusion Influenza-like illness are mainly due to influenza virus infection and the infections mainly concentrated in the months from September to December.Primary schools and middle schools are the target for prevention and control of outbreaks of influenza in Jining.