Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease. It is caused by the bacterium Bordetella pertussis. This illness primarily affects infants and young children but can strike at any age. The characteristic symptom of pertussis is a severe cough that can last for weeks or even months. The “whooping” sound is often heard when the person with pertussis tries to inhale after a coughing fit.