Detection Of Viral Pathogens And Analysis Of Respiratory Syncytial Virus In Hospitalized Children With Acute Lower Respiratory Tract Infection In Fuzhou

Objective:1.The aim of this study is through investigating the epidemiological data of hospitalized children with acute lower respiratory tractinfection in Fuzhou area,the composition and epidemicpattern of respiratory tract virus,to provide valuable epidemiological data for clinical diagnosis and treatment.2.The study is to explore the relevant data of genotype variation in RSV epidemic strains,and to investigate the epidemiological characteristics of RSV in children with acute lower respiratory tract infection(ALRTI)in Fuzhou,to predict the dominant subtypes and genotypes in the next epidemic season.It provides new useful information for the prevention and control of RSV and the development of antiviral drugs and vaccines.Methods: We collected nasopharyngeal secretions samples from hospitalized children with ALRTI in two hospitals in Fuzhou during the period of Jan.2018 to Jan.2019.The specimens were tested by immunofluorescent assay,including seven antigens of RSV,Influenza A virus(IFVA),Influenza B virus(IFVB),Human adenovirus(HAdV),and parainfluenza virus type1/2/3(PIV1/2/3).Positive samples were randomly selected for cell culture and the cytopathic effect of the virus was studied.During the period of Jan.2018 to Jan.2019,56 RSV positive samples were randomly selected.The second high variable region(HVR2)of G protein gene C-terminal in strains were sequenced by PCR and Sanger sequencing.DNAMAN software was used to align the multiple sequences and calculate homology.MEGA7.0 software was employed to calculate genetic distance,construct phylogenetic tree and analyze variations of RSV genotypes.By focusing on the epidemic characteristics of viral pathogens in children with ALRTI during the study period and combining with the epidemic situation in the past two years,the continuous changes of respiratory virus in Fuzhou area were analyzed.Results: From Jan.2018 to Jan.2019,we collected 2435 nasopharyngeal secretions samples from hospitalized children with ALRTI,and 487 positive samples(20.0%)were detected.Among the positive samples,there were 392 RSV cases,37 IFVA cases,4 IFVB cases,37 HAdV cases,3 PIV1 cases,4 PIV2 cases and 19 PIV3 cases.RSV was the main pathogen,which was 80.5% of all positive samples.In 487 positive cases,9 cases(1.8%)were complicated infection,including 2(RSV+HAdV)cases,2(RSV+IFVA)cases,3(RSV+IFVB)cases,1(RSV+PIV2)case and 1(RSV+PIV3)case.The majority of children with virus infection were younger than 2 years old.From Jan.2018 to Jan.2019,positive samples were detected every month and RSV infection was predominant(the average rate was 16.1%).Infections occurred mainly in spring and winter,and there were two peaks in Mar.2018 and Dec.2018 respectively.The positive rate of RSV reached the highest level(27.3%)in Dec.2018,and the lowest level in Jul.2018.Secondly,there was a small peak of IFVA infection in Jan.2019.The CPE of Hep-2 cells infected by virus were observed under microscope.56 RSV positive samples were randomly selected for PCR amplification.Of the 45 specimens with targeted bands,there were 32 cases of subtype A(65.3%)of),12 cases of subtype B(21.4%).The amplification products of G gene of subtype A and B were sequenced and analyzed by two-way nucleotide sequencing.The nucleotide identities of 32 isolates of subtype A(except for a single FZ32609)were 87.8% ~ 100%,and amino acid identities were 83.5% to 100%.Of the 32 isolates of RSV subtype A,30(93.8%)belonged to ON 1.Of the 12 isolates of RSV subtype B 9 strains belonged to BA11 type.The nucleotide identities were 97.9% ~ 100%,and amino acid identities were 50.9% to 100%.Conclusion: From Jan.2018 to Jan.2019,the positive rate of respiratory virus was 20.0% in hospitalized children with acute lower respiratory tract infection in Fuzhou.RSV was the most common pathogen,about 80.5%.Infections occurred mainly in spring and winter,and there was a peak in Mar.2018 and Dec.2018 each other.The infection rate of RSV reached the highest level(27.3%)in Dec.2018.Secondly,there was a small peak of IFVA infection in Jan.2019.There was no obvious epidemic peak of infection(HAdV,IFVB,PIV1/2/ 3)during Jan.2018 to Jan.2019.The results of sequencing and electrophoresis showed that both subtype A and B were found in the children with RSV infection duringJan.2018 to Jan.2019,but subtype A was the main prevalent subtype and ON1 was the dominate enotype.Based on the analysis of epidemic characteristics in 2016 and 2017 in Fuzhou,the pathogen of RSV infection had changed from subtype B to subtype A,indicating that the genotype change of RSV had taken place in the three consecutive epidemic years in this region.