Respiratory syncytial virus load predicts disease severity in previously healthy infants

J Infect Dis. 2005 Jun 1;191(11):1861-8. doi: 10.1086/430008. Epub 2005 Apr 21.


Background: Elucidating the relationship between viral load and respiratory syncytial virus (RSV) disease severity is critical to understanding pathogenesis and predicting the utility of antivirals.

Methods: Previously healthy, naturally RSV-infected infants <24 months old not treated with ribavirin, passive antibody, or corticosteroids were prospectively studied (n=141). Viral loads were measured by fresh quantitative culture from nasal washes collected at a single time point shortly after hospitalization.

Results: The subjects' mean age was 112.1 days, and the mean estimated gestational age at birth was 38.38 weeks. RSV load decreased with longer durations of symptoms before specimen collection (P=.01). Male subjects had higher RSV loads than female subjects (P=.036). Significant independent predictors of longer hospitalization were congenital anomaly (P<.0001), lower weight on admission (P=.028), and higher nasal RSV load (P=.008). A 1-log higher RSV load predicted a 0.8-day longer hospitalization. Lower weight and higher RSV load were also independently associated with respiratory failure (P<.0005 and P=.0049, respectively) and requirement for intensive care (P=.0007 and P=.0048, respectively).

Conclusions: In previously healthy infants, higher RSV loads measured at capturable time points after symptom onset predict clinically relevant measures of increased disease severity.

MeSH terms

  • Female
  • Humans
  • Infant
  • Male
  • Prospective Studies
  • Respiratory Syncytial Virus Infections / physiopathology*
  • Respiratory Syncytial Virus Infections / virology*
  • Respiratory Syncytial Viruses / isolation & purification*
  • Risk Factors
  • Severity of Illness Index
  • Viral Load*