The BUG project: Nasal microbiota, bronchiolitis and air pollution

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory infections in children under 5 years of age worldwide. The severity of RSV infection is partly explained by known risk factors, including medical comorbidities and young age. However, most infants hospitalized with RSV have been reported to be previously healthy and without predisposing risk factors for severe disease. This indicates that additional risk factors, such as environmental ones, like air pollution, contribute to the severity of the disease and may influence the inflammatory cascade leading to RSV infection, disease development, and exacerbation in infants. In addition, air pollution exposure has been related with worsening of respiratory diseases in both adults and children. Several studies have investigated the potential impact of respiratory microbiota on infections, which can interact with each other. In this context, the endogenous microbiota stabilizes during the first year of life and is subject to constant interspecies interactions. The potential role of the respiratory tract microbiota in influencing host responses has been suggested for RSV infection as well, with interactions between RSV and the nasopharyngeal microbiota observed to modulate the host immune response and potentially affect disease severity. The nasopharyngeal microbiota of 110 infants affected by bronchiolitis and 49 age- and gender-matched exhibiting no symptoms of ongoing inflammatory processes was characterized by 16S rRNA-based metagenomics sequencing,