Pertussis, also known as whooping cough, is an acute respiratory tract infection caused by the bacterium Bordetella pertussis. After an incubation period of 9 to 10 days, the clinical symptoms of the disease start with a catarrhal phase followed by paroxysmal cough and ending with persistent cough and whooping. The cough and whooping are characteristic of the diseases and make the clinical diagnosis easy to establish.