A Study On Viral Etiology Of 389 Children Under 5 Years Old With Acute Bronchiolitis

Objective Bronchiolitis causes great disease burden of children,so this research analyzes related viral etiology of 389 hospitalized children under 5 years old with acute bronchiolitis from January 2015 to December 2015,thus a preliminary understanding of epidemiology in various viruses and immune response of the host infected with different RSV subtypes can provide reference for the diagnosis and therapy or the prevention and control of clinical disease.Methods 1.We collected the nasopharyngeal swab specimens of 389 hospitalized children under 5 years old with acute bronchiolitis in Children's hospital of Chenzhou during January 2015 to December 2015,and then using direct immunofluorescence assay(DIF)to detect seven respiratory viral antigen(including RSV,ADV,IFV-A,IFV-B,PIV-I,PIV-II,and PIV-III)in these nasopharyngeal swab specimens.At last,we analyzed the epidemiological characteristics of seven respiratory viruses.2.For the children diagnosed with RSV infection in nasopharyngeal swab specimens,we identified its viral type and detected the expression level of the type 1 cytokine(IFN-? and IL-2),the type 2 cytokine(IL-4 and IL-13),the type 17 cytokine(IL-17)and the inhibitory cytokine(IL-10)in plasma of them.Then,we compared the epidemiological characteristics of two subtypes of RSV and the cytokine expression level in plasma of children infected with different RSV subtypes.Results 1.In this research,we detected 7 respiratory viral antigen in 389 nasopharyngeal swab specimens of children under 5 years old hospitalized with acute bronchiolitis,and among them,the rate of RSV was highest(41.9%),and the rate of other viruses were 8.2%(PIV-III),6.7%(ADV),3.1%(IFV-A),2.3%(IFV-B),1.8%(PIV-I),and 1.0%(PIV-II),respectively.The total rate of 7 viruses which had been detected was 65.0%,and the cases which had not been checked out occupied 136(35.0%).2.For age distribution,the total rate of 7 viruses which had been detected decreased with the increasing of age(the total rate of 7 detected viruses in four age groups were respectively 67.7%,66.4%,65.9%,and 56.7%);the rate of RSV was highest compared with the rate of other viruses in four age groups,and among 163 RSV positive cases,infants under 6 months as the highest proportion occupied 36.8%,and infants less than 3 years old occupied 88.3%;the high-risk age of other viruses: ADV was >1 year old and ?3 years old,IFV-A was >3 years old and ?5 years old,IFV-B was >1 year old and ?3 years old,PIV-I was ?6 months or >3 years old and ?5 years old,PIV-II was >6 months and ?1 year old,and PIV-III was ?1 year old.3.For the seasonal distribution,the rate of RSV was the highest in each season,and the high-occurrence season of RSV was in winter and spring;the high-occurrence season of ADV was in summer;the highoccurrence season of IFV-A was in summer,and IFV-B as the winter and spring;the high-occurrence seasons of PIV-I and PIV-II were all in winter,and PIV-III as the summer.4.For acute bronchiolitis patients with RSV infection,the subtypes distribution of RSV between two age groups(?6 months and > 6 months)showed no statistical difference;and RSV B subtype was the prevalent subtype of RSV infection during four seasons;besides,the expression of IL-10 in plasma of RSV A infected children was significantly lower than the level in plasma of RSV B infected children,while the level of other cytokines(including IFN-?,IL-2,IL-4,IL-13,and IL-17)between two groups showed no statistical difference.Conclusion 1.RSV is the main viral factor in causing acute bronchiolitis for children under 5 years old,and the high-occurrence season of RSV is in winter and spring,besides,the susceptibility population of RSV is infants within 6 months;the onset of RSV infection is mostly within 3 years old,and the onset of RSV infection after 3 years old is rare.2.During our study year,RSV B subtype is the prevalent subtype of RSV infected infants with acute bronchiolitis,and the RSV subtypes distribution between two age groups(?6 months and > 6 months)shows no statistical difference.3.RSV infection caused by two subtypes leads to the different immune status of the host,and the characteristic of this difference is that the expression level of IL-10 in plasma of RSV A infected children is significantly lower than the level in plasma of RSV B infected children.