pertussis

Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis, a gram-negative coccobacillus that produces toxins damaging the ciliated respiratory epithelium and causing profound lymphocytosis through impaired lymphocyte homing. The disease progresses through three stages—catarrhal, paroxysmal, and convalescent—with the classic presentation of severe coughing fits followed by an inspiratory whoop and post-tussive vomiting, though infants may present atypically with apnea rather than whooping and carry the highest mortality risk. Medical students must recognize that diagnosis is most often missed during the highly infectious catarrhal stage when symptoms mimic a common cold, that lymphocytosis on CBC should raise suspicion for pertussis, and that macrolides like azithromycin are first-line treatment while Tdap vaccination during each pregnancy is critical for protecting vulnerable newborns through passive antibody transfer.