Author: Julian Orenstein, M.D. Educational Pearls Colorado has a high population of unvaccinated children, and is at increased risk for pertussis outbreaks. The causative organism is Bordetella pertussis. It causes  causes respiratory epithelial necrosis leading to congestion of the bronchioles, leading to cough. The cough is unique - it is usually a series of expiratory coughs followed by one deep inspiration The clinical presentation is divided into 3 phases: Catarrhal: cough and congestion with low-grade fever and coryza. Whooping: characteristic cough. Resolution: recovery with persistent cough. Infants may not get this presentation, but may get apnea and nonspecific cough.   Tongue depressor can be used to elicit cough for diagnosis. References: Tozzi AE, Pastore Celentano L, Ciofi degli Atti ML, Salmaso S. Diagnosis and management of pertussis. CMAJ : Canadian Medical Association Journal. 2005;172(4):509-515. doi:10.1503/cmaj.1040766.