an acute, highly contagious infection of the respiratory tract, most frequently affecting young children, usually caused by Bordetella pertussis; a similar illness has been associated with infection by B. parapertussis and B. bronchiseptica. It is characterized by a catarrhal stage, beginning after an incubation period of about two weeks, with slight fever, sneezing, running at the nose, and a dry cough. In a week or two the paroxysmal stage begins, with the characteristic paroxysmal cough, consisting of a deep inspiration, followed by a series of quick, short coughs, continuing until the air is expelled from the lungs; the close of the paroxysm is marked by a long-drawn, shrill, whooping inspiration, due to spasmodic closure of the glottis. This stage lasts three to four weeks, after which the convalescent stage begins, in which paroxysms grow less frequent and less violent, and finally cease. Called also whooping cough.