Prolonged viral shedding as a marker of severity in respiratory syncytial virus bronchiolitis

Background and Objectives Respiratory syncytial virus (RSV) is responsible for most cases of acute viral bronchiolitis (AVB) in childhood. The association of factors such as RSV subtype, viral load, and viral coinfection with severe disease is controversial. The objective is to describe the viral load dynamics of RSV in children under 2 years with AVB, including the first viral load, peak viral load, viral decay, and any possible association with severe disease. Methods 73 inpatients with AVB and confirmed RSV infection were included. Viral load was obtained through nasal swab samples daily during hospitalization and weekly after discharge until absence of detection. Results 44 of the patients were male, the mean age was 5.76 months, and comorbidities were found in 15 (20.5%) of the patients. 54 (74%) of the patients had the peak viral load between the 4th and the 7th day of symptom onset. The mean duration of viral detection was 12.5 days. There was no association between the first and peak viral load with markers of severe disease. However, association was found between viral persistence exceeding 10 days and the following factors: longer hospitalization period (p=0.009), length of ventilation support (p=0.044), length of invasive mechanical ventilation (p=0.035), prolonged requirement of nutritional support (p=0.038), and a longer course of antibiotic treatment (p=0.024). Age was inversely correlated with most of the severity outcomes. Conclusion Despite the lack of association between RSV viral load values and disease severity, prolonged viral shedding was associated with several adverse outcomes, which can contribute to a better understanding of RSV disease, particularly as several interventions are anticipated to become available in the coming years.