Etiology surveillance and analysis of influenza in Ningxia during 2009-2013

Objective To investigate the epidemic situation and the virus types distribution in Ningxia during July. 2009-June. 2013 so as to provide a scientific basis for the prevention and control of influenza. Methods The throat swab specimens from influenza-like illness( ILI) were collected from national level influenza surveillance sentinel hospital,and then detected by RT-PCR method. Data was statistically analyzed. Results A total of 17 785 ILI samples were collected and tested,3 325 samples showed nucleic acid testing positive,with an overall positive rate as 18. 70%. In all of these positive specimens,the influenza A( H1N1),the seasonal influenza H3N2,H1N1 and the influenza B were respectively accounted for 49. 41%,26. 02%,0. 72% and 23. 85%. Age distribution data of the influenza positive rate showed that the 15 year-old group had the highest positive rate as 24. 20%,and the second higher was the 5 year-old group as 22. 28%. In addition,the peak seasons of influenza in four surveillance years mainly appeared in Winter and Spring. Conclusion Influenza A,especially the H1N1 was the dominant strain in Ningxia area during 2009-2013. Teens and school-age children were the high-risk population for the influenza. Winter and Spring were the flu high-occurrence season. And the constitute of the influenza subtype had changed after the period of H1N1 influenza pandemic in 2009.