Session: Poster Session: Respiratory Viruses I: Influenza and RSV
Tuesday, October 28, 2008: 12:00 AM
Room: Hall C
Background: Some studies suggest that RSV viral load is associated with illness severity. We compared RSV viral load among children hospitalized with LRTI vs. symptomatic and asymptomatic control children. Methods: During two respiratory seasons (Oct. 2005 - Sept. 2007) we obtained a nasopharyngeal swab (NPS) on children <3 years old hospitalized with LRTI. We also obtained a NPS on non-hospitalized children with no onset of respiratory symptoms within 3 days, primarily in Year 2. Samples were placed in RNA stabilizing buffer and frozen until tested. Viral load (shown as median log10) was determined by quantitative real-time polymerase chain reaction (PCR). Results: 102/440 (23%) of cases and 26/649 (4%) of controls were PCR-positive for RSV. 222 (34%) of control children had respiratory symptoms within 2 weeks. RSV viral load was higher in hospitalized cases, 7.16 (n=82), than RSV-positive controls, 6.45 (n=23) (p<0.001). Among hospitalized cases, RSV viral load was higher in Year 1, 7.45 (n=48) than in Year 2, 6.66 (n=34) (p<0.001). RSV viral load decreased with age in Year 1 (p for trend =0.011) but not Year 2. Higher viral load was associated with severity and symptom onset in Year 2: asymptomatic controls (6.22) < symptomatic controls (6.45) < hospitalized, symptom onset >48 hours (6.56) < hospitalized, symptom onset <48 hours (6.67) (p for trend=0.008). In hospitalized cases there was no difference in viral load by illness severity (mechanical ventilation, oxygen use, or length of stay >5 days). Conclusions: RSV viral load was higher in symptomatic than asymptomatic control children, higher in hospitalized cases than controls, and higher in cases with recent symptom onset. Viral quantitation may add value to interpretation of RSV diagnostic tests.