Relationship Between RSV Subtypes, Co-detections, Viral Load And Clinical Severity In Hospitalized Infants With Bronchiolitis

PART1ANALYSIS RSV SUBTYPES AND CO-DETECTIONS ONCLINICAL SEVERITY OF HOSPITALIZED INFANTS WITHBRONCHIOLITISObjective：Bronchiolitis is a common, acute, contagious respiratoryillness of infants that involves the lower respiratory tract. The relationshipbetween RSV subgtypes or RSV co-detections and clinical severity has notbeen studied very well. Our objective was to explore the relationshipbetween RSV subtypes or RSV co-detections with other viruses andclinical severity in hospitalized infants associated with bronchiolitis.Methods: From June2009to February2013, nasopharyngealaspirates were collected from the inpatients with respiratory tract infectionand etiologic tests on nasopharyngeal aspirates samples from each patientwere performed by PCR. We used the clinical score to estimate the symptoms and severity of bronchiolitis. Clinical informations werecollected for statistic analysis.Results: There were4501cases totally,2125were detected by16respiratory viruses, and454were associated with bronchiolitis. Of454infants, respiratory viruses positive were detected in389(85.7%) patients,of which, single virus was detected in208(45.8%) patients, two or moreviruses were detected in181(39.9%) patients. RSV was the most commonidentified virus with positive rate61.4%, followed by PIV (19.6%), HRV(16.1%), IV (13.4%), HBoV (13.4%), ADV (4.2%), HMPV (3.3%) andCoV (1.3%). It was easier to have fever in infants with RSVA singledetection positive than those of RSVB single detection positive. There wereno difference between RSVA single detection positive and RSVB singledetection positive groups in the clinical scores (P=0.19), in inducingrespiratory failure (P=0.11) and in durations of hospitalization (P=0.32).There were no difference between RSV single detection positive and RSVco-detections positive groups in the clinical scores (P=0.61), in inducingrespiratory failure (P=0.91) and in durations of hospitalization (P=0.95).Conclusion: RSV was the predominant virus detected in infantshospitalized with bronchiolitis. RSV subtypes as well as RSV co-detectionsdid not appear to increase risk for bronchiolitis severity. PART2ASSESSMENT OF DYNAMIC RSV VIRAL LOAD ONCLINICAL SEVERITY OF HOSPITALIZED INFANTS WITHBRONCHIOLITISObject: A higher RSV load has been reported to correlate withclinical severity, but few report concerns about the relationship between theclinical severity and RSV load dynamic change in China. Our objectivewas to explore the impact of dynamic RSV load on the clinical severity inthe course of hospitalized infants associated with bronchiolitis.Methods: Children≤24months old who were diagnosed withbronchiolitis within96hours of onset were prospectively enrolled in thestudy. Nasopharyngeal aspirates were obtained in a standardized mannerfrom each patient upon admission and on day3, day5and day7in hospital.RSV load was quantified by real-time fluorescence quantitative PCR forRSV subtype A and B at different time point shortly after hospitalization.We used the clinical score to estimate the symptoms and severity ofbronchiolitis.Results: A total of60children were enrolled,40of whom weredetected with RSV (31were RSVB,9were RSVA) and6of whom weredetected with other respiratory viruses; in14children, no virus wasdetected. There was positive correlation between RSV and clinical score (r2=0.121and P＜0.0001). The peak RSV load was observed on day1anddeclined subsequently. Infants in severe group tended to have higher RSVload than moderate and mild group, and moderate group tended to havehigher RSV load than mild group. The declines in mean viral loadscorrelate with the timing of onset of the declines in mean symptom scores.Conclusion: Dynamic RSV load was associated with the clinicalseverity of bronchiolitis in hospitalized infants. The higher in mean RSVload, the higher in mean clinical score, the more severe in disease withlonger duration of hospitalization and symptoms.