Analysis of the feature of influenza epidemic in Jiangsu province, 2006 to 2007

Objective　To investigate the feature of influenza epidemic in Jiangsu province from 2006 to 2007. Methods　The analysis were conducted on the data of the cases of influenza-like illness (ILI) collected from the sentinel hospitals of national level, the virus isolation results and the data of influenza or ILI outbreaks in the province. Results　In 2006 and in 2007 (week 1-52), a total of 94 231 and 102 099 ILI cases were registered in four sentinel hospitals in Xuzhou, Nanjing, Wuxi and Danyang, accounting for 4.67% and 4.87%, respectively, the difference of which was with significance statistically (I/Isup2/sup= 85.18, IP/I=0.0000).The proportion of ILI in Xuzhou, Nanjing, Wuxi, and Danyang were 7.18%, 5.06%, 3.66%, and 2.00%, respectively. As for the influenza or ILI outbreaks during 2006 and 2007, samples were collected for laboratory testing for 56 outbreaks (94.92%), with the positive rate of 92.86% (52 outbreaks). B influenza virus was predominated in 2006 (94.12%), while H3N2 (66.67%) and B (33.33%) viruses predominated in 2007. The outbreaks distributed from January to May and from September to December with the peaks between January and March (45 outbreaks, 86.54%). Large scale outbreak of B influenza (Victoria lineage) occurred in January and February, 2006 and large scale outbreak of H3N2 influenza occurred in January, 2007. Conclusion　Influenza activity in Jiangsu from 2006 to 2007 was stable, but with local outbreaks. Virus isolation results of the cases from sentinel hospitals and during the outbreaks indicated that H3N2 and B/Victoria lineage viruses predominated. Therefore, further research is needed on the changes of influenza activity and the development of the warning mechanisms.