Outpatient visit due to influenza like illness in 2 sentinel hospitals in Jinhua, Zhejiang,2009-2012

Objective s To understand incidence of influenza like illness (ILI) and estimate the disease burden caused by ILI in Jinhua. Methods The surveillance data of ILI from 2009 to 2012 in 2 sentinel hospitals in Jinhua were collected and analyzed. Results During 2009-2010 influenza season, the average proportion of ILI in outpatients was 3.67%, the RT-PCR positive rate of influenza virus nucleic acid detection was 23.89%, the estimated influenza infection rate was 22.59% and the influenza cases accounted for 8.29‰ of the outpatient visit in 2 sentinel hospitals. During 2010-2011 influenza season, the average ILI proportion was 1.90%, the RT-PCR positive rate of influenza virus nucleic acid detection was 8.42%, the estimated influenza infection rate was 6.27% and the Influenza cases accounted for 1.19‰ of the outpatient visit in 2 sentinel hospitals. During 2011-2012 influenza season, the average ILI proportion was 2.79%, the RT-PCR positive rates of influenza virus nucleic acid detection was 23.14%, the estimated influenza infection rate was 25.40% and the influenza cases accounted for 7.09‰ of the outpatient visit in 2 sentinel hospitals. The peak of RT-PCR positive detection curve and the peak of outpatient visit due to ILI were consistent during 3 influenza seasons, which mainly occurred during winter-spring. Except 2010-2011 influenza season, the ILI proportions in other 2 influenza seasons were higher than non influenza seasons. Conclusion Outpatient visit due to ILI mainly occurred during winter-spring in Jinhua. It is important to improve influenza surveillance and conduct ILI pathogen spectrum surveillance to reduce disease burden caused by ILI.