title: Respiratory syncytial virus genomic load and disease severity among children hospitalized with bronchiolitis: multicenter cohort studies in the United States and Finland.
abstract: BACKGROUND
  We investigated whether children with a higher respiratory syncytial virus (RSV) genomic load are at a higher risk of more-severe bronchiolitis.
  
  
  METHODS
  Two multicenter prospective cohort studies in the United States and Finland used the same protocol to enroll children aged <2 years hospitalized for bronchiolitis and collect nasopharyngeal aspirates. By using real-time polymerase chain reaction analysis, patients were classified into 3 genomic load status groups: low, intermediate, and high. Outcome measures were a length of hospital stay (LOS) of ≥3 days and intensive care use, defined as admission to the intensive care unit or use of mechanical ventilation.
  
  
  RESULTS
  Of 2615 enrolled children, 1764 (67%) had RSV bronchiolitis. Children with a low genomic load had a higher unadjusted risk of having a length of stay of ≥3 days (52%), compared with children with intermediate and those with high genomic loads (42% and 51%, respectively). In a multivariable model, the risk of having a length of stay of ≥3 days remained significantly higher in the groups with intermediate (odds ratio [OR], 1.43; 95% confidence interval [CI], 1.20-1.69) and high (OR, 1.58; 95% CI, 1.29-1.94) genomic loads. Similarly, children with a high genomic load had a higher risk of intensive care use (20%, compared with 15% and 16% in the groups with low and intermediate genomic loads, respectively). In a multivariable model, the risk remained significantly higher in the group with a high genomic load (OR, 1.43; 95% CI, 1.03-1.99).
  
  
  CONCLUSIONS
  Children with a higher RSV genomic load had a higher risk for more-severe bronchiolitis.
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School.
authors.forename: Kohei
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Pediatrics, Turku University Hospital, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Jartti
authors.affiliation: Department of Medicine, Boston Children's Hospital, Massachusetts.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Mansbach
authors.affiliation: Department of Infectious Disease, Arnold Palmer Hospital for Children, Orlando, Florida.
authors.forename: Federico R
authors.initials: FR
authors.lastname: Laham
authors.affiliation: Department of Molecular Virology and Microbiology and Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jewell
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School.
authors.forename: Janice A
authors.initials: JA
authors.lastname: Espinola
authors.affiliation: Department of Molecular Virology and Microbiology and Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Piedra
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Camargo
mesh_terms: D001988:Bronchiolitis / Q000473:pathology*; D002675:Child, Preschool; D015331:Cohort Studies; D003422:Critical Care / Q000706:statistics & numerical data; D005260:Female; D005387:Finland; D006801:Humans; D007223:Infant; D007902:Length of Stay; D008297:Male; D009305:Nasopharynx / Q000821:virology; D011446:Prospective Studies; D012367:RNA, Viral / Q000032:analysis* / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012121:Respiration, Artificial / Q000706:statistics & numerical data; D018357:Respiratory Syncytial Virus Infections / Q000473:pathology* / Q000821:virology*; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics / Q000302:isolation & purification*; D013223:Statistics as Topic; D014481:United States; D019562:Viral Load
chemical_list: D012367:RNA, Viral
keywords: bronchiolitis; children; cohort study; genomic load; hospitalization; infants; intensive care unit; length of stay; mechanical ventilation; respiratory syncytial virus