With the expanded scope of the guideline to infants with unexpected deterioration and/or admission to ICU, there is a recommendation to consider obtaining blood tests (e.g., Full Blood Count (FBC), C‐Reactive Protein (CRP), Procalcitonin (PCT) and blood cultures) for the diagnosis of serious bacterial co‐infection for infants with unexpected deterioration during hospitalisation or being admitted to ICU with bronchiolitis. Here, CRP is linked to bronchiolitis.