IL36A and bronchiolitis: In human nasal epithelial cells grown in vitro under air-liquid interface we found IL-36α to be produced by epithelial cells during RSV infection and that its secretion is enhanced by neutrophils.<h4>Conclusions</h4>These findings implicate mucosal IL-36α as a dominant feature of severe paediatric bronchiolitis.<h4>One sentence summary</h4>Mucosal transcriptomics identifies IL-36 secretion as a feature of life-threatening paediatric RSV and all-cause bronchiolitis associated with interferon response failure.