Analysis of influenza surveillance from 2000 to 2007 in Gansu province

Objective To study the epidemical characteristics of influenza in Gansu province from 2000 to 2007, and to discuss the changes of the predominant strains of influenza virus. This study provide scientific basis for defending influenza effectively. Methods Influenza surveillance, collecting the pharyngeal swab specimens from influenza patients of national surveillance hospital and unsure influenza epidemic situations, inoculated on MDCK cell culture to obtain the influenza virus strains. Results 2001.10--2007.12,coUecting the 6383 specimens,943 influenza virus strains were isolated, positive rate was 14.77 %, 218 strains were A1 (H1N1), 352 strains were A3 (H3N2) ,312 strains were B subtype of Victoria and 61 strains were B subtype of Yamagata. There were totally 61 outbreak of influenza-like cases were observed in Gansu Province during the last 5 years,44 cases were isolated influenza virus, of 38 cases were caused by B subtype of Victoria virus strains, 3 cases were caused by H3N2,2 cases were caused by B subtype of Yamagata virus strains, 1 cases were caused by H1N1. Conclusion Influenza is active in human population. Influenza type A virus is predominant in winter and type B virus rsulted in the outbreak in school and kidsgarden from March to June in the last 3 years. Key words: Influenza surveillance; Case report; Orthomyxoviridae