Epidemiological Characteristics And Genomic Sequence Analysis Of Human Avian Influenza A(H7N9) Virus Infection In Zhejiang Province From 2013 To 2015

Objective:To investigate the epidemiological characteristics and genomic sequences of human infections with avian influenza A(H7N9)virus in Zhejiang province from 2013 to 2015 and explore the viral mutations and molecular characteristics.Methods:Epidemiology and clinical surveys were conducted for acute respiratory infection(ARI)cases monitored by eight sentinel hospitals in Zhejiang province from 2013 to 2015,and their respiratory tract specimens were collected for influenza virus detection.ARI cases were classified into positive and negative group with H7N9 virus,analyzing their clinical and epidemiologic characteristics respectively.15 positive specimens with H7N9 infection were randomly selected and sequenced for genes,other sequences related to H7N9 influenza A virus in China were collected from GenBank or GISAID,Genetic and phylogenetic analyses were performed by MEGA6.0 software.At the same time the Protean software module in DNAStar was applied to forecast the HA and NA protein of B lymphocyte antigen epitope.And Phymol software was used to simulate spatial structure for the amino acid sequence variation in HA and NA protein.Results:1.7602 severe acute respiratory infection cases were recruited from eight hospitals,including 106(1.4%)cases of laboratory confirmed H7N9 in Zhejiang province from 2013 to 2015,two obvious epidemic peaks were noticed,in April,2013 and January to February,2014.Age Median(M)of the enrolled cases with H7N9 was 59 year-old,males accounted for 66%.30 cases were dead,including 20 males and 10 females.Chronic underlying diseases(including chronic heart,kidney,liver,nervous system diseases)in H7N9 positive group were higher than influenza-negative group,the differences were statistically significant(P<0.05).2.Compared to influenza-negative group,those who infected with H7N9 virus were more likely to occur Yellow phlegm,haemoptysis,central nervous system symptom,X-ray/CT abnormal and lung auscultation abnormal,and the total number of white blood cells,lymphocytes and platelets were lower in H7N9 infectors than influenza-negative group,being statistically significant(P<0.05).3.The homology of HA and NA genes of human H7N9 virus strains comparing with the same time domestic reference strains(including poultry disease strains)was high in Zhejiang province from 2013 to 2015,HA and NA amino acid system evolutionary tree can be roughly divided into three groups,the strains isolated in different years were have some difference of gene sequence,indicated that the virus was in continuous variation.Viral amino acid variation showed that HA protein of all 15 representative strains had 226(Q226L/I)and 186(G186V)receptor binding sites mutation,all strains isolated from 2015 had A134V mutation;2 strains with R294K mutation in NA protein;9 strains with E627K mutation and 1 strain with D701N mutation in PB2 protein;all strains had S31N mutation in M2 and 1368V in PB1.All HA cleavage sites were PEIPKGR↓GLF,which indicated low pathogenic strain,while glycosylation sites mutation of HA and NA protein were not found.4.The Protean software module in DNAStar is applied to forecast the HA protein for B cell surface antigen epitope section were:172-183,214-220,313-322,374-381,393-399,466-473,492-505,and in NA protein B cell surface antigen epitope section were:46-52,206-210,220-225,323-328,332-345,366-373,380-387.Conclusions:1.Outbreaks usually occurred in winter and spring in Zhejiang province.The aged peoples especially with chronic underlying disease were at high risk of avian influenza A(H7N9)virus infection.2.H7N9 patients proned to have severe symptoms and the total number of white blood cells,lymphocytes and platelet often declined.3.The homology of HA and NA genes of human H7N9 virus strains comparing with the same time domestic reference strains was high in Zhejiang province from 2013 to 2015,Strains had some significant mutations of amino acid in protein,indicated that the virus was in continuous variation.4.This experiment uesd DNAStar software to forecast the antigen epitope of H7N9 avian influenza virus,in the following research work,we will joint a variety of bioinformatics tools to further analysis,and will verify the antigenicity and specificity of our result.