In very young infants severity of acute bronchiolitis depends on carried viruses

PLoS One. 2009;4(2):e4596. doi: 10.1371/journal.pone.0004596. Epub 2009 Feb 25.


Background: RT amplification reaction has revealed that various single viruses or viral co-infections caused acute bronchiolitis in infants, and RV appeared to have a growing involvement in early respiratory diseases. Because remaining controversial, the objective was to determine prospectively the respective role of RSV, RV, hMPV and co-infections on the severity of acute bronchiolitis in very young infants.

Methods and principal findings: 209 infants (median age: 2.4 months) were enrolled in a prospective study of infants <1 year old, hospitalized for a first episode of bronchiolitis during the winter epidemic season and with no high risk for severe disease. The severity was assessed by recording SaO(2)% at admission, a daily clinical score (scale 0-18), the duration of oxygen supplementation and the length of hospitalization. Viruses were identified in 94.7% by RT amplification reaction: RSV only (45.8%), RV only (7.2%), hMPV only (3.8%), dual RSV/RV (14.3%), and other virus only (2%) or coinfections (9%). RV compared respectively with RSV and dual RSV/RV infection caused a significant less severe disease with a lower clinical score (5[3.2-6] vs. 6[4-8], p = 0.01 and 5.5[5-7], p = 0.04), a shorter time in oxygen supplementation (0[0-1] days vs. 2[0-3] days, p = 0.02 and 2[0-3] days, p = 0.03) and a shorter hospital stay (3[3-4.7] days vs.6 [5-8] days, p = 0.001 and 5[4-6] days, p = 0.04). Conversely, RSV infants had also longer duration of hospitalization in comparison with RSV/RV (p = 0.01) and hMPV (p = 0.04). The multivariate analyses showed that the type of virus carried was independently associated with the duration of hospitalization.

Conclusion: This study underlined the role of RV in early respiratory diseases, as frequently carried by young infants with a first acute bronchiolitis. RSV caused the more severe disease and conversely RV the lesser severity. No additional effect of dual RSV/RV infection was observed on the severity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Disease
  • Bronchiolitis / pathology
  • Bronchiolitis / virology*
  • Hospitalization
  • Humans
  • Infant
  • Infant, Newborn
  • Length of Stay
  • Metapneumovirus / isolation & purification
  • Prospective Studies
  • Respiratory Syncytial Virus, Human / isolation & purification
  • Reverse Transcriptase Polymerase Chain Reaction
  • Viruses / isolation & purification*