AKT-0764
A 4-year-old boy from a traveller community family is brought to the surgery by his mother.
She informs you that he began with what appeared to be a severe catarrhal cold, but now experiences intense paroxysms of coughing, causing him to turn completely red in the face and struggle to catch his breath. Upon examination, he has no fever.
What feature on history, examination, or investigation, although not conclusive, is consistent with the presence of whooping cough?