| Objective:Influenza is an acute respiratory infection caused by Influenza Virus(IV).It can cause worldwide prevalence.This study was aimed,from epidemiology,molecular biology,serology and other aspects,to analyze the epidemic characteristics of influenza in Zhenjiang area,and to provide scientific basis for the prediction of vaccine control effect in this area and the prevention and control of influenza epidemics.Methods:1.The samples of influenza-like illness were collected from 2014 to 2016 in Zhenjiang area for type identification by qRT-PCR.The corresponding monitoring data was derived from the "China influenza surveillance information system",and the epidemiological statistical analysis was carried out in combination with the laboratory res?Lts.2.Virus isolation was performed on positive samples of IV nucleic acid to obtain epidemic strains.The HA and NA genes were amplified and then sequenced.The sequences were spliced,compared,and analyzed by bioinformatics software.The WHO recommended vaccine strains in the Northern Hemisphere and representative strains inside and outside Jiangsu Province were used for comparison and tracing.3.The levels of A(H1N1)pdm09,A(H3)and B(BY/BV)IV antibodies in healthy people of different age were detected and analyze.Results:1.The prevalence of IV in Zhenjiang area from 2014 to 2016 was seasonal,with peak incidence in winter and spring and small epidemics in summer.The three-year epidemic strains were dominated by the alternating prevalence of A(H1N1)pdm09,A(H3)and B(BY/BV).There was no difference in the sensitivity of IV to gender,but the rate of positive infection was still the highest among people above 60 and 5 years old.All seven municipalities have IV detections.2.The HA and NA nucleotide identities of the 13 isolates of the A(H1N1)pdm09 Strains with the vaccine strain A/California/07/2009 were all above 95.6%.The HA germ line evolution analysis showed that the 7 strains were closely related to the Jiangsu Province Strain A/Jiangsu-Danyang/SWL1836/2014,and 1 strain was highly homologous to the vaccine strain.Evolutionary analysis of NA lineages showed that 9 strains were clustered with vaccine strains.Compared with HA amino acid loci of the vaccine strain,K173 Q mutation occurred in 11 strains in Sa area,and K181 E mutation occurred in 1 strain;V183I mutation occurred in 3 strains in Ca1 area,but no receptor binding site or glycosylation site was found.There was no variation of antigenicity.3.Compared with the 2014/2015 vaccine strain A/Texas/50/2012 and 2015/2016 vaccine strain A/Switzerland/9715293/2013,13 strains of A(H3)isolates maintained the nucleotide and amino acid homology of HA and NA at above 94.8%.HA germ line evolution analysis showed that 2 strains were highly homologous to the 2013/2015 vaccine strain A/Texas/50/2012,and 1 strain was homologous to the 2015/2016 vaccine strain A/Switzerland/9715293/2013.Evolutionary analysis of NA phylogenetic lines showed that 3 strains were closely related to the 2013/2015 vaccine strain A/Texas/50/2012.A total of 10 strains had mutations in multiple amino acid sites.However,the amino acid and glycosylation sites of relevant drug resistance sites were basically conserved.4.Among the 14 isolates of type B,the nucleotide and amino acid homology of HA and NA between BY were all above 95.2%,and that of BV was above 95.9%.Phylogenetic analysis revealed that two strains of HA-Y2/NA-V1 were reassortant and one strain of HA-V1/NA-Y2 was reassorted.Compared with the 2014/2015 vaccine strain B/Massachuts/2/2012,there were 5 strains of BY strains with 120-loop,150-loop,190 helix and other amino acid changes.Compared with the 2015/2016 vaccine strain B/Phuket/3073/2013,there were 5 strains with changes in the 120-loop,150-loop,and 190-helical amino acid sites.Compared with B/Brisbane/60/2008,there were 2 strains with 120-ring,150-ring and other amino acid changes in the BV strain and the vaccine strain B/Brisbane/60/2008.An I97 M mutation(190 helices)occurred.No mutations were detected in the active sites of NA isolates,but there were 4 new glycosylation sites 204 NET.5.The 1000 serum tests showed that the positive rate of anti-type IV antibody in healthy people was higher than that of anti-IBV antibody,and the difference was statistically significant.The protection rates of A(H1N1)pdm09,A(H3),BY,and BV antibodies were 24.4%,26.7%,28.4%,and 18.6% respectively,and the GMTs were 46.1,47.9,66.1,and 35.5 respectively.The overall level of antibody protection was low and the high titer antibodies were few.The positive rate,protective rate,and GMT value of all types of IV antibodies in the 5-year-old group and the 15-year-old group were significantly higher than those in the other three groups,while the values in the 60-year-old group and above were all lower.In addition,40.7% of the positive antibody population had the same individual multiple infections of different subtypes IV.Conclusion:1.From 2014 to 2016 in Zhenjiang area,IV showed a mixed prevalence of multiple subtypes,but the proportion of each subtype was different,suggesting that long-term IV monitoring is needed to further reveal its epidemic pattern.In the IV epidemic season,it is necessary to pay special attention to the elderly and children,strengthen the propaganda and education of IV prevention and control,use specific vaccines for specific age groups,and prevent the outbreak of group IV epidemics.2.The genetic polymorphisms of 13 strains of Zhenjiang A(H1N1)pdm09 isolates increased,no antigenic changes occurred,no mutations were found at the receptor binding sites and glycosylation sites.Homology analysis suggested that WHO recommended vaccine strain A/California/07/2009 still has a high degree of immune protection.3.The 13 strains of A(H3)isolates may have been caused by virus migration in other provinces.Some strains and vaccine strains were different.Although no new subtypes had been formed,their gene characteristics and antigenicity had undergone a certain degree of variation.The amino acid and glycosylation sites of the relevant drug resistance sites were basically conserved and were still sensitive to the currently used neuraminidase inhibitors.4.The 14 isolates of type B,HA-Y2/NA-V1 interline reassortment occurred in 2 isolates,and HA-V1/NA-Y2 interprogeny reassortment occurred in 1 isolate.Whether this inter-system reassortant strain will cause a local outbreak of IBV in this region needs further monitoring.There were point mutations in the 120-loop,150-loop,160-loop and 190 helices in the HA1 region of the antigenic epitopes,suggesting that the antigenicity of some strains was altered and the protective effect of the vaccine might be reduced.5.The overall protection level of A(H1N1)pdm09,A(H3)and BV subtype IV antibodies in the population was low,and there were few high-titer antibodies,indicating that the IV prevalence in this region is prone to occur.Therefore,while conducting IV epidemiology and etiological monitoring,we must continue to monitor the evolutionary characteristics of the population and the level of the population's IV immunity,and jointly analyze IV trends from multiple angles to provide scientific evidence for the prevention and control of IV. |
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