Respiratory syncytial virus and rhinovirus severe bronchiolitis are associated with distinct nasopharyngeal microbiota

To the Editor: Bronchiolitis is the leading cause of infant hospitalization in the United States,1 and cohort studies suggest that up to 50% of these hospitalized infants will develop childhood asthma.1 The 2 most common viral etiologies of severe bronchiolitis (ie, bronchiolitis requiring hospitalization) are respiratory syncytial virus (RSV) and rhinovirus (RV).1 Although these 2 viruses have been the focus of most previous cohorts examining the association between bronchiolitis and asthma, RSV and RV infect infants through a respiratory tract colonized with bacteria.2,3 Cross-sectional and prospective data suggest that the respiratory microbiota may also play a role in the development of childhood asthma.2 To date, no studies have examined the relationship between the respiratory viruses, RSV and RV, and the respiratory microbiota of infants hospitalized with bronchiolitis. [...]RV has many subtypes and may be either a bystander virus or a pathogen,9 but the observed RV-Proteobacteria profile suggests that in infants hospitalized with bronchiolitis, RV is not simply a bystander.