title: [Relationship between respiratory syncytial virus subtype and clinical severity in bronchiolitis].
abstract: BACKGROUND
  Respiratory syncytial virus (RSV) is the most frequently implicated agent in bronchiolitis. The virus presents two antigenic subtypes (A and B). The results of studies on the relationship between viral subtype and clinical severity are conflicting.
  
  
  OBJECTIVE
  To evaluate whether the subtype of this virus constitutes an independent variable in the severity of clinical expression of RSV infection.
  
  
  METHODS
  We prospectively studied previously healthy children aged less than 2 years admitted for RSV infection during an epidemic season. Clinical presentation and evolution, laboratory and radiological aspects were compared in subsets of children infected with RSV subtype A or B. Clinical severity parameters included score and duration of respiratory distress, oxygen requirements, admission to the intensive care unit, mechanical ventilation and length of hospital stay.
  
  
  RESULTS
  Eighty-five patients were enrolled in the study (50 boys and 35 girls; mean age 4.8,4.3 months). Fifty-nine children were infected with RSV subtype A. No differences were found in age, sex or antecedents but children with subtype B were less likely to have been breast-fed. Clinical presentation and laboratory and radiological findings were similar in both groups. No statistically significant differences in clinical severity parameters were found between subsets A and B. Age less than 3 months was associated with greater duration of respiratory distress and longer hospital stay.
  
  
  CONCLUSIONS
  The results do not support the hypothesis that subtype A infection is associated with more severe respiratory syncytial virus disease.
authors: Departamento de Pediatría. Hospital de San João. Oporto. Portugal. Joaobarreira@mail.telepac.pt
authors: J
authors: J
authors: Neves Barreira
authors: C
authors: C
authors: Fonseca
authors: M
authors: M
authors: Cardoso
authors: A
authors: A
authors: Azevedo
authors: A
authors: A
authors: Bonito Vítor
mesh_terms: D001988:Bronchiolitis / Q000821:virology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies; D012136:Respiratory Syncytial Viruses / Q000145:classification*; D012720:Severity of Illness Index