[Etiological analysis of influenza surveillance data in Xuzhou from 2005 to 2011].

To investigate the prevalence and subtypes of influenza viruses in Xuzhou city from 2005 to 2011 and to provide the scientific supports for influenza prevention and control in this religion.The throat swab samples were collected from the influenza-like cases from national influenza like illness sentinel hospital in Xuzhou. The samples were used for influenza virus isolation and identification, sent on the national flu center to confirm according to the "national influenza surveillance program" and "influenza virus and experimental technology".From Oct. 2005 to Dec. 2011, a total of 9561 swab specimens were collected in which 1152 strains were identified for influenza viruses with total isolated rate of 12.0%. Among these strains, 708 strains were A1 (H1N1) subtype (14.2%), 466 strains were A3 (H3N2) subtype (40.5%), 78 strains were new H1N1 subtype (6.8%), 362 strains were BV (Victoia) subtype (31.4%) and 82 strains were BY (Yamagate) subtype (7.1%). The top detection rate (25.9%) arose in 2007, secondary detection rate (17.4%) occurred at 2009 and the lowest one (2.3%) appeared in 2011. From the winter of 2005 to the spring of 2006 A1 (H1N1) subtype had appeared as predominant strains but in the winter of 2006 the predominant strains were BV subtype. It changed to A3 subtype in 2007 to 2009 and the other three dominant strains were A1, BV and BY in 2008. In the winter of 2009, both A3 (H3N2) and new H1N1 subtype were predominant strains. BV subtype was predominant strains in 2010 to 2011. The prevalence of A3 subtype appeared in all the year while prevalence of BV only arose in the spring and winter. So the detection rate was high in January (34.4%) but low in August (2.2%). The influenza population is correlated with age, the highest detection rate arose in 5-age group and the lowest detection rate appeared in 25-age group.Influenza subtype A1, A3, New H1N1 are all appeared as predominant strains in Xuzhou city from 2005 to 2010. Besides, the prevalence of BV subtype is stronger in recently.