Analysis On Pathogenic Surveillance Of Infulenza Virus In Qinghai Province In2010

Objective:To investigate the prevalence and type and subtype distribution of seasonal influenza virus and analyze the prevalent trends of influenza and hemagglutinin (HA) gene variation of subtype A/H3N2in Qinghai Province in2010. To understand the influenza strains variation discipline which would provide the protective effect assessment of WHO vaccine strains for general population in Qinghai province.Methods:The data of ILI (Influenza-like illness) were collected from16sentinel hospitals of6prefectures, one region and one city by Influenza surveillance information system in2010, and analyzed by Excel software. The nasopharyngeal swabs were collected from the ILI of sentinel hospitals, detected by real-time RT-PCR method, of which positive samples inoculated with MDCK cells and then identified by hemagglutination inhibition (HI) method.10strains of subtype H3influenza virus were analyzed with antigenic characteristic and sequenced with HA gene, and compared with vaccine strain recommended by WHO and some stains isolated from other province at the same time using the MEGA4.0software, then the phylogenetic tree were constructed by Neighor-Joining (NJ) method, which would provide the scientific evidence for studying HA genetic variation.Results:The ILI percent of national sentinel hospital and provincial sentinel hospitals was1.0%and11.42%respectively in Qinghai province in2011, and the children under5-years-old were infected most.2530nasopharyngeal swabs were collected from sentinel hospitals in Qinghai province, in which214cases were nucleic acid testing positive,64strains influenza virus were isolated from the specimens, including43strains of H3N2,15strains of type B and6strains of epidemic A/H1N1. The distribution of type and subtype were significantly different. It was shown that the HI titer had difference of4times by antigenic analysis of10strains of subtype H3influenza virus. After HA gene sequence analysis of H3N2, we knew that the sequences of10strains which isolated form Qinghai Province in2010were similar to that of isolated from Nanjing and far from vaccine strains recommended by WHO in2010, and not in the same branch of a tree.Conclusion:ILI peak were in mid-January and mid-December in Qinghai province in2010. During the influenza season, epidemic A (H1N1), B and A (H3N2) viruses existed at the same time, but A (H3N2) was advantage strain. The antigenic and genetic characteristics of10strains of H3N2virus had changed in Qinghai province in2010.