Surveillance of influenza in Shandong province, 2005-2011

Objective To understand the disease trend, virus type and activity level of influenza in Shandong from 2005 to 2011and provide scientific information for the surveillance and early warning of influenza. Methods The surveillance data of influenza like illness (ILI) and the detection Results of ILI cases' nasal swabs during this period were collected to conduct analysis. Results From 2005 to 2011, a total of 9 729 498 outpatients visited sentinel hospitals, of which 246 904 were ILI cases, accounting for 2.54%. The annual proportion of ILI cases was 2.78%, 2.02%, 1.82%, 2.05%, 3.84%, and 2.24%, respectively (P0.05). Up to 70.59% of ILI cases were children aged 0-5 years. Totally 10 901 samples from ILI cases were detected and 1563 strains of influenza viruses were isolated (14.3%). The annual positive rate was 13.8%, 19.2%, 26.4%, 13.7%, 24.8% and 5.5% respectively (P0.05). Spearman correlation analysis indicated that ILI rate and isolation rate of virus strain was positive correlated (r=0.293, P0.05). Conclusion Influenza virus was more active in 2009. The predominant strains changed regularly, The ILI incidence characteristics was similar to influenza virus activity.