• Milena De Paulis, Danielle Bruna Leal Oliveira, Luciano Matsumiya Thomazelli, Alexandre Archanjo Ferraro, Edison Luiz Durigon, and Sandra E Vieira.
• Unidade de Urgencia e Emergencia Referenciada Infantil, Divisao de Pediatria, Hospital Universitario, Universidade de Sao Paulo, Sao Paulo, SP, BR.
• Clinics (Sao Paulo). 2021 Jan 1; 76: e3192.

ObjectiveThe relationship between viral load and the clinical evolution of bronchiolitis is controversial. Therefore, we aimed to analyze viral loads in infants hospitalized for bronchiolitis.MethodsWe tested for the presence of human respiratory syncytial virus (HRSV) or human rhinovirus (HRV) using quantitative molecular tests of nasopharyngeal secretions and recorded severity outcomes.ResultsWe included 70 infants [49 (70%) HRSV, 9 (13%) HRV and 12 (17%) HRSV+HRV]. There were no differences among the groups according to the outcomes analyzed individually. Clinical scores showed greater severity in the isolated HRSV infection group. A higher isolated HRSV viral load was associated with more prolonged ventilatory support, oxygen therapy, and hospitalization days, even after adjustment for the age and period of nasopharyngeal secretion collection. In the co-infection groups, there was a longer duration of oxygen therapy when the HRSV viral load was predominant. Isolated HRV infection and co-infection with a predominance of HRV were not associated with severity.ConclusionHigher HRSV viral load in isolated infections and the predominance of HRSV in co-infections, independent of viral load, were associated with greater severity. These results contribute to the development of therapeutic and prophylactic approaches and a greater understanding of the pathophysiology of bronchiolitis.

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