MUC5AC and cystic fibrosis: Recent evidence from the Australian Respiratory Early Surveillance Team for CF (AREST CF) implicates mucin accumulation as the initial trigger of neutrophilic inflammation in the CF airway (4), and suggests respiratory viral infection may trigger the muco-inflammatory phenotype observed in CF since the heterogeneity of early CF lung disease mirrors the heterogeneity of childhood viral infection (5, 6).