These are less spontaneous than in typical respiratory infections. Infants under 6 mo often vomit in association with the cough, which leads to dehydration. Hypoxia tends to be more severe than the clinical appearance of the child suggests. A significant number will present with cyanosis and apneic spells. Vaccinated adults usually only develop a prolonged bronchitis without a whoop.
Unvaccinated adults are more likely to have whooping and post-tussive emesis.
On average they wait a median of 3 wk before seeking treatment. Hypoxia should be considered. Dehydration is common on presentation. Fever over 39 degrees C is rare. Bordetella pertussis .