Pertussis (Whooping Cough)

Pertussis is a toxin-mediated respiratory infection caused by Bordetella pertussis. After an average incubation of 5–10 days, illness commonly moves through catarrhal, paroxysmal, and convalescent stages. The catarrhal stage can look like an uncomplicated upper-respiratory infection: rhinorrhea, mild cough, and increasing cough frequency. The paroxysmal stage is more distinctive. Irritation and impaired clearance of the ciliated airway lining produce repeated bursts of forceful coughing. The patient may then make a high-pitched inspiratory whoop, vomit after coughing, or struggle to recover between episodes. The cough can persist into convalescence because injured airway epithelium and retained secretions recover slowly; persistent cough does not automatically mean that antimicrobial therapy has failed. A whoop is not required for recognition. Infants, particularly very young infants, may present with apnea, bradycardia, poor feeding, or cyanosis rather than the classic sound. Their limited respiratory reserve means that an apparently brief pause in breathing can become an emergency quickly.