Influenza surveillance in Anqing, Anhui, 2010-2014

Objective To understand the situation of influenza in Anqing, Anhui province, during 2010-2014 and provide evidence for influenza prevention and control. Methods Statistical analysis was conducted on the influenza surveillance data, collected from National Influenza System, in Anqing during this period, 2 test was conducted to analyze the surveillance and virus detection results. Results The overall proportion of influenza like illness (ILI) in Anqing during this period was 3.73% and the annual differences were significance (2=187.18, P0.05). ILI mainly occurred in age groups 0-1 years and 5-6 years, accounting for 54.45% and 28.86% respectively. The positive rate of nucleic acid detection in ILI cases was 6.92%, slightly lower than average level of Anhui province, and seasonal influenza A (H3) and B viruses were predominant. The annual differences in nucleic acid positive rate were significant (2=70.21, P0.05), while gender specific difference in nucleic acid positive rate was not significance (2=0.45, P0.05).The positive correlation was found between ILI and ILI% (r=0.55, P0.05) and between ILI% and the nucleic acid positive rate (r=0.43, P0.05). Conclusion Influenza activity level was low in Anqing from 2010 to 2014,but the seasonality was obvious with winter peak and summer peak, while the month when the peak occurred varied, especially in summer. Different subtypes of viruses circulated alternatively or concurrently. Influenza B mainly occurred in the winter, mainly affecting young children. The influenza virus activity was nearly consistent with the epidemiological characteristics of ILI.