Pertussis is a highly contagious illness of the respiratory mucous membrane. It’s marked by a series of short, violent coughs sometimes followed by a high-pitched intake of breath that sounds like whoop. A type of bacteria called Bordetella pertussis causes this infectious disease. The bacteria attach to the cilia (tiny, hair-like extensions) that line the upper respiratory system. Bordetella pertussis toxins (poisons) damage the cilia and cause airways to swell.