| OBJECTIVE:H3N2 outbreaks at different degree every year regularly.Current vaccine strains have no effective protection against the strains since its high variability.To investigate the epidemiological characteristics of Influenza virus A(H3N2)infection in Hangzhou,Zhejiang Province from 2010 to 2015,monitor the molecular changes of the virus,and finally we provide the scientific evidence for the prevention and control of the disease.METHODS:1.The data of the outbreak of H3N2 was collected from First Affiliated Hospital of Zhejiang University influenza surveillance network,the annual like cases were 2406,995,766,1156,1928 and 404,respectively.H3N2 influenza virus was isolated from throat swab samples of all the patients,and confirmed by the blood coagulation inhibition test and influenza virus nucleic acid detection.2.The fragments of full-length of H3N2 virus were designed according to the A/New York/392/2004(H3N2),and sequenced the samples of suspected patients.3.Sequences collection:all the sequences of HA and NA were acquired from GISAID and NCBI.The "H3N2","Asia","China","Hangzhou","HA" or "H3N2","Europe","Switzerland","HA","H3N2","North America","United States","texas’,"HA","H3N2","Oceania","Australia","Victoria","HA" were searched from GISAID.And the key words "H3N2","HA","NA" and "Hangzhou" were searched from NCBI.4.The sequences of HA and NA were screened and compared according to the address of separation,time and host.One sequence was chosed if the sequences were the same.The groups of H3N2 were divided as Hangzhou,and the strains recommended by WHO as A/TEXAs/50/2012(H3N2)\A/Victoria/361/2011 and A/Switzerland/9715293/2013 E5 3.All the sequences were edited and analyzed by Clustal X(v1.8),and phylogenetic tree were constructed by the method of Neighbor-joing with Mega(v5.2).RESULTS:1.The cases of positive patients during 2010～2015 were 73,42,4-,33,62 and 30,respectively,with the ratios were 3.03%,4.22%,5.67%,2.85%,3.77%and 4.34%.2.The infection rate analyses of Hangzhou showed that there was significant difference between different years(χ2=26.266,P<0.05).And the genders and ages made no difference(χ2=7.168,χ2=12.954,P>0.05).3.There was no new variants formed according to the sequences of HA1 during 2015.4.The NA gene during 2010～2013 was highly conserved.CONCLUSION:The positive tatio of Influenza A virus(H3N2)during 2010～2015 in Hangzhou was 46.9%,and the majority of the virus strains belong to the 3C group.Different as that there was an epidemic peak which existed in winter in the North China,every July to September,December to next March were the epidemic periods in Hangzhou.The vaccine strain A/Switzerland/9715293/2013 may not be able to provide protection for the epidemic group 3c.1a virus since there was very little antigenic cross between 3c.1a and 3c.2a virus strains.The analyze of the HA gene during Jan to Sep of 2015 showed that there were several mutations in many sites of A and B zones of antigenic determinant.It disclosed that the mutation was enhanced even there was no new variants formed.We also analyzed the NA sequences of H3N2 during year 2010～2013,it is highly conserved,the evolution is mainly based on the evolution of an evolutionary trunk.There was no gradual process on the evolutionary tree and presented evolutionary leap.The strains of the same age belonged to several branches exist at the same time,these clades in the phylogenetic tree position was varied.Some branches will become evolutionary mainstream since the evolution due to stress and immunity. |
PDF Full Text Request