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Objective To examine influenza -related excess mortality in Ningbo City from 2010—2014.Methods Data related to death and virology were collected from surveillance system of Ningbo Center for Disease Control and Prevention from 2010 to 2014.Rate differential model was used for data analysis to calculate excess mortality caused by five different cause of death.Results The duration of influenza prevalence was about 37 weeks from 2010 to 2014.The prevalent influenza strains from 2010—2013 were type B,H1NI and H3N2,and the prevalent influenza strains in 2014 were H1NI and H3N2 .From 2010 to 2014,for all cause of death (AC),the average influence -related excess mortality per week was 2.54 per 100 000 in Ningbo City.In five influence seasons,the average influence -related excess mortality for AC were 12.66 /100 000,15.19 /100 000,27.86 /100 000,12.66 /100 000 and 25.32 /100 000,respectively.The average influence -related excess mortality for five cause of death (PI,RC,IHD,COPD,AC)were 1.68 /100 000,12.83 /100 000,1.34 /100 000,0.84 /100 000 and 18.74 /100 000.During 5 monitoring years,annual excess mortality of≥65 group were more higher than that of total population,and annual excess mortality of 0 -4 group were lower than that of total population.Conclusion Influenza was prevalent mainly in winter and spring.The excess mortality resulted from influenza was high.Vaccinating people older than 65 and chronic cardiovascular patients could reduce the risk.
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<p><b>OBJECTIVE</b>To investigate the epidemiological characteristics of influenza B viruses and explore the genetic evolution characteristics of the hemagglutinin(HA) and neuraminidase(NA) genes of local isolated strains in Ningbo, Southeast China, during 2010 to 2012.</p><p><b>METHODS</b>Respiratory specimens from 3440 cases of patients with influenza-like illness(ILI) during 2010 to 2012 were collected in for virus isolation. And the 628 sera samples were collected in 2010 from the healthy community population to detect the HI antibody level against the local isolated virus.For phylogenetic analysis, the fragments of HA and NA genes were amplified and sequenced from strains isolated in different years. The association between evolution of HA and epidemiological characteristics were analyzed.</p><p><b>RESULTS</b>A total of 109 strains of influenza B virus were isolated, including 102 (93.6%) Victoria-lineage strains and 7 (6.4%) Yamagata-lineage strains. Positive rates of HI antibody against Victoria-lineage strains and Yamagata-lineage strains were 51.1% (321) and 47.8% (300), respectively (χ(2) = 1.405, P > 0.05) among the 628 sera samples. The phylogenetic analysis showed that all HA fragments of isolated strains clustered the same branch with Malaysia/2506/2004 while the NA genes formed different branches. Compared with Brisbane/60/2008 strain, there were 1 to 5 Amino acid mutations in HA domain, and more mutations were detected in NA domain, ranged from 6 to 16 sites. The genetic evolution of NA in Victoria-lineage strains were faster compared with HA.</p><p><b>CONCLUSION</b>The genetic evolution rates of NA genes were faster than that of HA genes in the local circulated Victoria-lineage viruses during 2010 to 2012;The comprehensive analysis of HA and NA fragments were more reliable and sensitive on surveillance of genetic evolution of influenza B viruses.</p>